Day_51.java

// Spiral Matrix
class Solution {
    public List<Integer> spiralOrder(int[][] matrix) {
        int n = matrix.length;
        int m = matrix[0].length;
        List<Integer> ans = new ArrayList<>();
        int left = 0, top = 0, right = m - 1, bottom = n - 1;
        while(left<=right && top<=bottom){
            for(int i=left;i<=right;i++){
                ans.add(matrix[top][i]);
            }
            top++;
            for(int i=top;i<=bottom;i++){
                ans.add(matrix[i][right]);
            }
            right--;
            if(top<=bottom){
                for(int i=right;i>=left;i--){
                    ans.add(matrix[bottom][i]);
                }
                bottom--;
            }

            if(left<=right){
                for(int i=bottom;i>=top;i--){
                    ans.add(matrix[i][left]);
                }
                left++;
            }
        }
        return ans;
    }
}

// Spiral Matrix II
class Solution {
    public int[][] generateMatrix(int n) {
        int[][] matrix = new int[n][n];
        int left = 0, top = 0, right = n - 1, bottom = n - 1, num = 1;
        while(left<=right && top<=bottom){
            for(int i=left;i<=right;i++){
                matrix[top][i] = num;
                num++;
            }
            top++;
            for(int i=top;i<=bottom;i++){
                matrix[i][right] = num;
                num++;
            }
            right--;
            if(top<=bottom){
                for(int i=right;i>=left;i--){
                    matrix[bottom][i] = num;
                    num++;
                }
                bottom--;
            }

            if(left<=right){
                for(int i=bottom;i>=top;i--){
                    matrix[i][left] = num;
                    num++;
                }
                left++;
            }
        }
        return matrix;
    }
}