PG0004.Question02

[jack81722]

Introduction

根據題目實作3x3矩陣(Matrix)結構的下列方法:

public struct Matrix3x3
{
    public float this[int index];
    public float this[int row, int col];
    public float[,] To2DArray();
}

Answer

答案

最後的To2DArray，也能建立一個新的Array，然後用迴圈一個一個塞值也可以，
答案中的寫法是C#的System Lib提供的工具，寫起來挺方便的。

public struct Matrix3x3
{
    /// <summary>
    /// Inner matrix
    /// </summary>
    private float[,] _matrix;

    #region -- Properties --
    public float m00
    {
        get { return _matrix[0, 0]; }
        set { _matrix[0, 0] = value; }
    }

    public float m01
    {
        get { return _matrix[0, 1]; }
        set { _matrix[0, 1] = value; }
    }

    public float m02
    {
        get { return _matrix[0, 2]; }
        set { _matrix[0, 2] = value; }
    }

    public float m10
    {
        get { return _matrix[1, 0]; }
        set { _matrix[1, 0] = value; }
    }

    public float m11
    {
        get { return _matrix[1, 1]; }
        set { _matrix[1, 1] = value; }
    }

    public float m12
    {
        get { return _matrix[1, 2]; }
        set { _matrix[1, 2] = value; }
    }

    public float m20
    {
        get { return _matrix[2, 0]; }
        set { _matrix[2, 0] = value; }
    }

    public float m21
    {
        get { return _matrix[2, 1]; }
        set { _matrix[2, 1] = value; }
    }

    public float m22
    {
        get { return _matrix[2, 2]; }
        set { _matrix[2, 2] = value; }
    }
    #endregion

    /// <summary>
    /// Get/Set an element by 1D-Index
    /// </summary>
    public float this[int index]
    {
        get
        {
            int row = index / 3;
            int col = index % 3;
            return _matrix[row, col];
        }
        set
        {
            int row = index / 3;
            int col = index % 3;
            _matrix[row, col] = value;
        }
    }

    /// <summary>
    /// Get/Set an element by row and colomn
    /// </summary>
    public float this[int row, int col]
    {
        get
        {
            return _matrix[row, col];
        }
        set
        {
            _matrix[row, col] = value;
        }
    }

    #region -- Constructors --
    public Matrix3x3(params float[] array)
    {
        if (array == null || array.Length != 9)
        {
            throw new ArgumentException("Array length must be equal to 9");
        }
        _matrix = new float[3, 3];
        for (int i = 0; i < array.Length; i++)
        {
            _matrix[i / 3, i % 3] = array[i];
        }
    }

    public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
    {
        _matrix = new float[,]
        {
            {m00, m01, m02 },
            {m10, m11, m12 },
            {m20, m21, m22 },
        };
    }
    #endregion

    /// <summary>
    /// Parse matrix into 2D-Array
    /// </summary>
    /// <returns>Parsed 2D-Array</returns>
    public float[,] To2DArray()
    {
        var newArr = new float[3, 3];
        Array.Copy(_matrix, newArr, 9);
        return newArr;
    }
}

[SoonYu97]

小鲨 (程式)

答案

public class Question2
{
    public struct Matrix3x3
    {
        /// <summary>
        /// Inner matrix
        /// </summary>
        private float[,] _matrix;

        #region -- Properties --
        public float m00
        {
            get { return _matrix[0, 0]; }
            set { _matrix[0, 0] = value; }
        }

        public float m01
        {
            get { return _matrix[0, 1]; }
            set { _matrix[0, 1] = value; }
        }

        public float m02
        {
            get { return _matrix[0, 2]; }
            set { _matrix[0, 2] = value; }
        }

        public float m10
        {
            get { return _matrix[1, 0]; }
            set { _matrix[1, 0] = value; }
        }

        public float m11
        {
            get { return _matrix[1, 1]; }
            set { _matrix[1, 1] = value; }
        }

        public float m12
        {
            get { return _matrix[1, 2]; }
            set { _matrix[1, 2] = value; }
        }

        public float m20
        {
            get { return _matrix[2, 0]; }
            set { _matrix[2, 0] = value; }
        }

        public float m21
        {
            get { return _matrix[2, 1]; }
            set { _matrix[2, 1] = value; }
        }

        public float m22
        {
            get { return _matrix[2, 2]; }
            set { _matrix[2, 2] = value; }
        }
        #endregion

        /// <summary>
        /// Get/Set an element by 1D-Index
        /// </summary>
        public float this[int index]
        {
            get
            {
                return _matrix[index / 3, index % 3];
            }
            set
            {
                _matrix[index / 3, index % 3] = value;
            }
        }

        /// <summary>
        /// Get/Set an element by row and colomn
        /// </summary>
        public float this[int row, int col]
        {
            get
            {
                return _matrix[row, col];
            }
            set
            {
                _matrix[row, col] = value;
            }
        }

        #region -- Constructors --
        public Matrix3x3(params float[] array)
        {
            if (array == null || array.Length != 9)
            {
                throw new ArgumentException("Array length must be equal to 9");
            }
            _matrix = new float[3, 3];
            for (int i = 0; i < array.Length; i++)
            {
                _matrix[i / 3, i % 3] = array[i];
            }
        }

        public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
        {
            _matrix = new float[,]
            {
                {m00, m01, m02 },
                {m10, m11, m12 },
                {m20, m21, m22 },
            };
        }
        #endregion

        /// <summary>
        /// Parse matrix into 2D-Array
        /// </summary>
        /// <returns>Parsed 2D-Array</returns>
        public float[,] To2DArray()
        {
            float[,] result = new float[3, 3];
            for (int i = 0; i < result.Length; i++)
            {
                result[i / 3, i % 3] = _matrix[i / 3, i % 3];
            }
            return result;
        }
    }
}

[A24575255]

JIA（程式新手）

我的答案

public float this[int index]
{
    get => _matrix[index / 3, index % 3];
    set => _matrix[index / 3, index % 3] = value;
}
public float this[int row, int col]
{
    get => _matrix[row, col];
    set => _matrix[row, col] = value;
}
public float[,] To2DArray()
{
    float[,] array = new float[3, 3];
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            array[i, j] = _matrix[i, j];
        }
    }
    return array;
}

[OLDShaw1022]

老蕭OLDShaw（程式）

我的答案

public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get
                {
                    return _matrix[index / 3, index % 3];
                }
                set
                {
                    _matrix[index / 3, index % 3] = value;
                }
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
                set
                {
                    _matrix[row, col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                float[,] result = new float[3, 3];
                for (int x = 0; x < 3; x++)
                {
                    for (int y = 0; y < 3; y++)
                    {
                        result[x, y] = _matrix[x, y];
                    }
                }
                return result;
            }
        }
    }

測試截圖

不知道To2DArray() Reference轉換用手填來省效能有沒有必要。

[jack81722]

這做法是可行的，本來作法就不只有一種
而且確實會比回圈的方式好一點

[louise-bwsx]

小4 ( 程式 )

Details

            public float this[int index]
            {
                get
                {
                    return _matrix[index / 3, index % 3];
                }
                set
                {
                    _matrix[index / 3, index % 3] = value;
                }
            }

            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
                set
                {
                    _matrix[row, col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            public float[,] To2DArray()
            {
                float[,] temp = new float[3, 3];
                for (int i = 0; i < 3; i++)
                {
                    Debug.Log("i:" + i);
                    for (int j = 0; j < 3; j++)
                    {
                        Debug.Log("j:" + j);
                        temp[i, j] = _matrix[i, j];
                    }
                }
                return temp;
            }

沒碰過matrix感覺像是固定length的多維陣列
笑死 寫了老半天才發現return 錯的東西 想說結果怎麼還是一樣

話說有沒有辦法讓測試過程快一點? 每次跑測試都會play過一次
我本來想說用enter play mode加快 但會有Error
這樣的話感覺我自己用monobehavior 加 odinInspector的[Button]跑出的結果反而比較快

[jack81722]

這個測試方式確實比較麻煩，
一般來說，測試只需要在IDE執行就差不多了，
Unity提供的測試框架有整合進他們的編輯器，
也可能是為了方便測試在動態的情境下一些狀況，
目前比較熟知的就是這套做法，
往好處想，他幫你把測試結果的UI做出來了（只是很醜）

[cliffleecl]

Cliff Lee CL (程式、專案管理)

我的答案

public class Question2
{
    public struct Matrix3x3
    {
        /// <summary>
        /// Inner matrix
        /// </summary>
        private float[,] _matrix;

        #region -- Properties --
        public float m00
        {
            get { return _matrix[0, 0]; }
            set { _matrix[0, 0] = value; }
        }

        public float m01
        {
            get { return _matrix[0, 1]; }
            set { _matrix[0, 1] = value; }
        }

        public float m02
        {
            get { return _matrix[0, 2]; }
            set { _matrix[0, 2] = value; }
        }

        public float m10
        {
            get { return _matrix[1, 0]; }
            set { _matrix[1, 0] = value; }
        }

        public float m11
        {
            get { return _matrix[1, 1]; }
            set { _matrix[1, 1] = value; }
        }

        public float m12
        {
            get { return _matrix[1, 2]; }
            set { _matrix[1, 2] = value; }
        }

        public float m20
        {
            get { return _matrix[2, 0]; }
            set { _matrix[2, 0] = value; }
        }

        public float m21
        {
            get { return _matrix[2, 1]; }
            set { _matrix[2, 1] = value; }
        }

        public float m22
        {
            get { return _matrix[2, 2]; }
            set { _matrix[2, 2] = value; }
        }
        #endregion

        /// <summary>
        /// Get/Set an element by 1D-Index
        /// </summary>
        public float this[int index]
        {
            get => _matrix[Get1DRow(index), Get1DCol(index)];
            set => _matrix[Get1DRow(index), Get1DCol(index)] = value;
        }

        int Get1DRow(int index)
        {
            return index / _matrix.GetLength(0);
        }
        
        int Get1DCol(int index)
        {
            return index % _matrix.GetLength(1);
        }

        /// <summary>
        /// Get/Set an element by row and colomn
        /// </summary>
        public float this[int row, int col]
        {
            get => _matrix[row, col];
            set => _matrix[row, col] = value;
        }

        #region -- Constructors --
        public Matrix3x3(params float[] array)
        {
            if (array == null || array.Length != 9)
            {
                throw new ArgumentException("Array length must be equal to 9");
            }
            _matrix = new float[3, 3];
            for (int i = 0; i < array.Length; i++)
            {
                _matrix[i / 3, i % 3] = array[i];
            }
        }

        public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
        {
            _matrix = new float[,]
            {
                {m00, m01, m02 },
                {m10, m11, m12 },
                {m20, m21, m22 },
            };
        }
        #endregion

        /// <summary>
        /// Parse matrix into 2D-Array
        /// </summary>
        /// <returns>Parsed 2D-Array</returns>
        public float[,] To2DArray()
        {
            // Deep copy _matrix to avoid changing the original matrix
            var result = new float[_matrix.GetLength(0), _matrix.GetLength(1)];
            for (int i = 0; i < _matrix.GetLength(0); i++)
            {
                for (int j = 0; j < _matrix.GetLength(1); j++)
                {
                    result[i, j] = _matrix[i, j];
                }
            }
            return result;
        }
    }
}

[angus945]

答案

public float this[int index]
{
    get
    {
        int x = index / 3;
        int y = index % 3;
        return _matrix[x, y];
    }
    set
    {
        int x = index / 3;
        int y = index % 3;
        _matrix[x, y] = value;
    }
}
public float this[int row, int col]
{
    get
    {
        return _matrix[row, col];
    }
    set
    {
        _matrix[row, col] = value;
    }
}
public float[,] To2DArray()
{
    float[,] array = new float[3, 3];
    Array.Copy(_matrix, array, array.Length);
    return array;
}

[jane901201]

Tina( Unity程式 | 佛系劇本 )

我的答案

using System;
using System.Linq.Expressions;

namespace PG0004.Questions
{
    public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get
                {
                    switch (index)
                    {
                        case 0: return _matrix[0, 0];
                        case 1: return _matrix[0, 1];
                        case 2: return _matrix[0, 2];
                        case 3: return _matrix[1, 0];
                        case 4: return _matrix[1, 1];
                        case 5: return _matrix[1, 2];
                        case 6: return _matrix[2, 0];
                        case 7: return _matrix[2, 1];
                        case 8: return _matrix[2, 2];
                        default: return default;
                    }
                }
                set
                {
                    switch (index)
                    {
                        case 0: _matrix[0, 0] = value; break;
                        case 1: _matrix[0, 1] = value; break;
                        case 2: _matrix[0, 2] = value; break;
                        case 3: _matrix[1, 0] = value; break;
                        case 4: _matrix[1, 1] = value; break;
                        case 5: _matrix[1, 2] = value; break;
                        case 6: _matrix[2, 0] = value; break;
                        case 7: _matrix[2, 1] = value; break;
                        case 8: _matrix[2, 2] = value; break;
                    }
                }
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
                set
                {
                    _matrix[row, col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                float[,] temp =  new float[3,3];
                
                Array.Copy(_matrix, temp, _matrix.Length);
                
                return temp;
            }
        }
    }
}

然後看了解答後，才知道原來 this[int index] 那邊還能那樣寫，這樣就不用回傳 default 或 null，但有時就是會遇到資料傳回來是 null 的情況，不知道除了用 if 擋掉外有沒有比較好的做法…

[jack81722]

設計一些比較底層的邏輯時，幫使用者思考避免踩到坑確實是個課題，
不過在這個情境中，如果遇到超出範圍的數值，
我會選擇噴出錯誤而不是回傳default（我偷懶），
這不是一個合理的input，不合理的input也不應該丟出合理的結果，
因為使用者會以為這些都是正常的使用，
反而會導致後續更嚴重的開發問題，
這時候會考慮增加一個Function（例如：TryGet等）去增加使用者的手段
或是在註解中提到可能的錯誤

[vre343434]

七七(程式)

我的答案

public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get
                {
                    int x = index / 3;
                    int y = index % 3;
                    return _matrix[x, y];
                }
                set
                {
                    int x = index / 3;
                    int y = index % 3;
                    _matrix[x, y] = value;
                }
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get { return _matrix[row, col]; }
                set { _matrix[row, col] = value; }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(
                float m00,
                float m01,
                float m02,
                float m10,
                float m11,
                float m12,
                float m20,
                float m21,
                float m22
            )
            {
                _matrix = new float[,]
                {
                    { m00, m01, m02 },
                    { m10, m11, m12 },
                    { m20, m21, m22 },
                };
            }
            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                float[,] array = new float[3, 3];
                Array.Copy(_matrix, array, array.Length);
                return array;
            }
        }

（¯﹃¯）

[YouSyuan]

Syuan

我的答案

public class Question2
    {
        public struct Matrix3x3
        {
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion
            public float this[int index]
            {
                get
                {
                    return _matrix[index / 3, index % 3];
                }
                set
                {
                    _matrix[index / 3, index % 3] = value;
                }
            }

            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
                set
                {
                    _matrix[row, col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            public float[,] To2DArray()
            {
                float[,] copy_data = new float[3, 3];
                for(int i = 0; i < 9; ++i)
                {
                    copy_data[i / 3, i % 3] = _matrix[i / 3, i % 3];
                }
                return copy_data;
            }
        }
    }

[BolingCan]

罐頭（程式）

我的答案ヾ(•ω•`)o

namespace PG0004.Questions
{
    public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --

            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }

            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get => _matrix[index / _matrix.GetLength(0), index % _matrix.GetLength(0)];
                set => _matrix[index / _matrix.GetLength(0), index % _matrix.GetLength(0)] = value;
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get => _matrix[row, col];
                set => _matrix[row, col] = value;
            }

            #region -- Constructors --

            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }

                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21,
                float m22)
            {
                _matrix = new float[,]
                {
                    { m00, m01, m02 },
                    { m10, m11, m12 },
                    { m20, m21, m22 },
                };
            }

            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                float[,] array = new float[_matrix.GetLength(0), _matrix.GetLength(1)];
                Array.Copy(_matrix, array, array.Length);
                return array;
            }
        }
    }
}

不知道有沒有可以寫更好的地方，但寫得很快樂O(∩_∩)O

[jefflin0424]

肥羊(程式)

我的答案

public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get
                {
                    int x = index / 3; //index0-0,index1-1,index2-2,index3-1,index4-1,index6-2,index7-2 
                    int y = index % 3; //index0-0,index1-1,index2-2,index3-0,index4-1,index6-0,index7-1
                    return _matrix[x, y];
                }
                set
                {
                    int x = index / 3;
                    int y = index % 3;
                    _matrix[x, y] = value;
                }
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
                set
                {
                    _matrix[row, col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                float[,] newArray = new float[3, 3];

                Array.Copy(_matrix, newArray, newArray.Length);

                return newArray;
            }
        }
    }

[ISnoweve]

Snoweve (程式)

我的答案

         public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get
                {
                    int x = index / 3;
                    int y = index % 3;
                    return _matrix[x, y];
                }
                set
                {
                    int x = index / 3;
                    int y = index % 3;
                    _matrix[x, y] = value;
                }
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
                set
                {
                    _matrix[row, col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                float[,] array = new float[3, 3];
                Array.Copy(_matrix, array, array.Length);
                return array;
            }
        }
    }

<<反饋>>

[TWEdward]

TWEdward(新人/程式/企劃)

我的答案

public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get
                {
                    if (index < 0 || index >= 9)
                        return 0;
                    return _matrix[index/3, index%3];
                }
                
                set
                {
                    if(index >= 0 && index < 9)
                        _matrix[index/3,index%3]=value;
                }
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get
                {
                    if (row < 0 || row >= 3 || col < 0 || col >= 3)
                        return 0;
                    return _matrix[row,col];
                }
                set
                {
                    if(row >= 0 && row < 3 && col >= 0 || col < 3)
                        _matrix[row,col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                float[,] arrayCopy = new float[3, 3];
                Array.Copy(_matrix,arrayCopy,_matrix.Length);
                return arrayCopy;
            }
        }
    }

解題心得感想

感覺這題我寫的沒有很好，只能先求能跑能動能通過單元測試就好，透過IDE的提示功能有看到throw......Exception()等等選項可以選，但是因為還沒有很了解，我會再研究看看!!

[jack81722]

基本都沒錯，可以自信點，把感覺拿掉（X)
再不久之後應該就會講錯誤處理相關的東西了

[s32436515]

肉鬆（程式 / 音樂）

我的答案

　　public struct Matrix3x3
        {
            public float this[int index]
            {
                get
                {
                    int tempRow = index / 3;
                    int tempCol = index % 3;
                    return _matrix[tempRow, tempCol];
                }
                set
                {
                    int tempRow = index / 3;
                    int tempCol = index % 3;
                    _matrix[tempRow, tempCol] = value;
                }
            }

            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
            }
            
            public float[,] To2DArray()
            {
                float[,] outputArr = new float[3, 3];
                for(int i = 0; i < outputArr.Length; i++)
                {
                    outputArr[i / 3, i % 3] = _matrix[i / 3, i % 3];
                }
                return outputArr;
            }
        }

課程回饋

感謝勞師的講解！
Q2實作有點卡在不知道要用 /3 和 %3 去取位置 (偷喵了一眼#)
這兩堂下來好多東東，感覺不太好吸收，希望以後實作多使用能更理解 > <

[dun047]

答案

    public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get
                {
                    int r = index / 3;
                    int c = index % 3;
                    return _matrix[r, c];
                }
                set
                {
                    int r = index / 3;
                    int c = index % 3;
                    _matrix[r, c] = value;
                }
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
                set
                {
                    _matrix[row, col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                var NewArray = new float[3, 3];
                Array.Copy(_matrix, NewArray, 9);
                return NewArray;
            }
        }
    }

回饋

在做這題的時候不太理解題目的目標，能理解數值與參照的不同，但要做什麼不太懂，看了答案，要使用
int r = index / 3;
int c = index % 3;
的原因不太了解，還請在解說一下
Array.Copy的方式好好用

[jack81722]

抱歉，過這麼久才回
我這邊還是解釋一下
這是將陣列轉換成二維結構的一種計算方式
二維陣列全部位置為可以參照下列:
0 1 2
3 4 5
6 7 8
一維陣列:
0 1 2 3 4 5 6 7 8

r是row，c是column的意思，換個思維想r是y軸座標，c是x軸座標
當我們有一個橫向N個column的二維陣列時
0N-1元素會放在第一列(第一個row)
N2N-1元素會放在第二列(第二個row)
實際舉例如果一個column為3的二維陣列
第5個元素就是5 / 3，又因為整數相乘會自動去除小數點
最後的結果就是第1列(初始為0)

剛剛也提到0~N-1元素放在第一列
所以我們要得到第k個元素放在哪個column位置(x座標)時
可以用取餘數的方式取得
舉例來說剛剛的第5個元素就是5 % 3，餘數是2

綜合上述，我們知道第五個元素會放在二維陣列中的第1列第2個位置
我們可以觀察到一維陣列被分為三個三個一組，實際上就是三個三個一列(row)

[MurasakiAurora]

極光（程式）

我的答案

public class Question2
    {
        public struct Matrix3x3
        {
            /// <summary>
            /// Inner matrix
            /// </summary>
            private float[,] _matrix;

            #region -- Properties --
            public float m00
            {
                get { return _matrix[0, 0]; }
                set { _matrix[0, 0] = value; }
            }

            public float m01
            {
                get { return _matrix[0, 1]; }
                set { _matrix[0, 1] = value; }
            }

            public float m02
            {
                get { return _matrix[0, 2]; }
                set { _matrix[0, 2] = value; }
            }

            public float m10
            {
                get { return _matrix[1, 0]; }
                set { _matrix[1, 0] = value; }
            }

            public float m11
            {
                get { return _matrix[1, 1]; }
                set { _matrix[1, 1] = value; }
            }

            public float m12
            {
                get { return _matrix[1, 2]; }
                set { _matrix[1, 2] = value; }
            }

            public float m20
            {
                get { return _matrix[2, 0]; }
                set { _matrix[2, 0] = value; }
            }

            public float m21
            {
                get { return _matrix[2, 1]; }
                set { _matrix[2, 1] = value; }
            }

            public float m22
            {
                get { return _matrix[2, 2]; }
                set { _matrix[2, 2] = value; }
            }
            #endregion

            /// <summary>
            /// Get/Set an element by 1D-Index
            /// </summary>
            public float this[int index]
            {
                get
                {     
                    int row = index / 3;
                    int col = index % 3;
                    return _matrix[row, col];
                }
                set
                {
                    int row = index / 3;
                    int col = index % 3;
                    _matrix[row, col] = value;
                }
            }

            /// <summary>
            /// Get/Set an element by row and colomn
            /// </summary>
            public float this[int row, int col]
            {
                get
                {
                    return _matrix[row, col];
                }
                set
                {
                    _matrix[row, col] = value;
                }
            }

            #region -- Constructors --
            public Matrix3x3(params float[] array)
            {
                if (array == null || array.Length != 9)
                {
                    throw new ArgumentException("Array length must be equal to 9");
                }
                _matrix = new float[3, 3];
                for (int i = 0; i < array.Length; i++)
                {
                    _matrix[i / 3, i % 3] = array[i];
                }
            }

            public Matrix3x3(float m00, float m01, float m02, float m10, float m11, float m12, float m20, float m21, float m22)
            {
                _matrix = new float[,]
                {
                    {m00, m01, m02 },
                    {m10, m11, m12 },
                    {m20, m21, m22 },
                };
            }
            #endregion

            /// <summary>
            /// Parse matrix into 2D-Array
            /// </summary>
            /// <returns>Parsed 2D-Array</returns>
            public float[,] To2DArray()
            {
                float[,] newArr = new float[3, 3];
                for(int x=0; x<3; x++)
                {
                    for(int y=0;y<3;y++)
                    {
                        newArr[x, y] = _matrix[x, y];
                    }
                }
                return newArr;
            }
        }
    }