Leetcode-solutions

A collection of LeetCode questions to ace the coding interview!

LeetCode Topics

Array

0001-two-sum
0018-4sum
0026-remove-duplicates-from-sorted-array
0027-remove-element
0031-next-permutation
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0036-valid-sudoku
0037-sudoku-solver
0039-combination-sum
0040-combination-sum-ii
0041-first-missing-positive
0042-trapping-rain-water
0045-jump-game-ii
0046-permutations
0047-permutations-ii
0049-group-anagrams
0051-n-queens
0053-maximum-subarray
0063-unique-paths-ii
0064-minimum-path-sum
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0075-sort-colors
0081-search-in-rotated-sorted-array-ii
0085-maximal-rectangle
0088-merge-sorted-array
0090-subsets-ii
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0118-pascals-triangle
0119-pascals-triangle-ii
0122-best-time-to-buy-and-sell-stock-ii
0123-best-time-to-buy-and-sell-stock-iii
0128-longest-consecutive-sequence
0134-gas-station
0135-candy
0139-word-break
0140-word-break-ii
0169-majority-element
0179-largest-number
0215-kth-largest-element-in-an-array
0218-the-skyline-problem
0219-contains-duplicate-ii
0220-contains-duplicate-iii
0229-majority-element-ii
0240-search-a-2d-matrix-ii
0260-single-number-iii
0307-range-sum-query-mutable
0315-count-of-smaller-numbers-after-self
0321-create-maximum-number
0324-wiggle-sort-ii
0327-count-of-range-sum
0330-patching-array
0334-increasing-triplet-subsequence
0376-wiggle-subsequence
0486-predict-the-winner
0493-reverse-pairs
0768-max-chunks-to-make-sorted-ii
0769-max-chunks-to-make-sorted
0810-chalkboard-xor-game
0853-car-fleet
0907-sum-of-subarray-minimums
0912-sort-an-array
0962-maximum-width-ramp
0975-odd-even-jump
1008-construct-binary-search-tree-from-preorder-traversal
1368-minimum-cost-to-make-at-least-one-valid-path-in-a-grid
1472-design-browser-history
1649-create-sorted-array-through-instructions

Hash Table

0001-two-sum
0017-letter-combinations-of-a-phone-number
0030-substring-with-concatenation-of-all-words
0036-valid-sudoku
0037-sudoku-solver
0041-first-missing-positive
0049-group-anagrams
0073-set-matrix-zeroes
0076-minimum-window-substring
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0126-word-ladder-ii
0127-word-ladder
0128-longest-consecutive-sequence
0133-clone-graph
0138-copy-list-with-random-pointer
0139-word-break
0140-word-break-ii
0141-linked-list-cycle
0142-linked-list-cycle-ii
0169-majority-element
0187-repeated-dna-sequences
0202-happy-number
0205-isomorphic-strings
0208-implement-trie-prefix-tree
0219-contains-duplicate-ii
0229-majority-element-ii
0352-data-stream-as-disjoint-intervals
0432-all-oone-data-structure
0460-lfu-cache

String

0006-zigzag-conversion
0008-string-to-integer-atoi
0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0028-find-the-index-of-the-first-occurrence-in-a-string
0030-substring-with-concatenation-of-all-words
0044-wildcard-matching
0049-group-anagrams
0072-edit-distance
0076-minimum-window-substring
0087-scramble-string
0091-decode-ways
0093-restore-ip-addresses
0097-interleaving-string
0115-distinct-subsequences
0126-word-ladder-ii
0127-word-ladder
0131-palindrome-partitioning
0132-palindrome-partitioning-ii
0139-word-break
0140-word-break-ii
0179-largest-number
0187-repeated-dna-sequences
0205-isomorphic-strings
0208-implement-trie-prefix-tree
0214-shortest-palindrome
0316-remove-duplicate-letters
0402-remove-k-digits
0449-serialize-and-deserialize-bst
0459-repeated-substring-pattern
0686-repeated-string-match
0796-rotate-string

Two Pointers

0018-4sum
0026-remove-duplicates-from-sorted-array
0027-remove-element
0028-find-the-index-of-the-first-occurrence-in-a-string
0031-next-permutation
0042-trapping-rain-water
0061-rotate-list
0075-sort-colors
0086-partition-list
0088-merge-sorted-array
0141-linked-list-cycle
0142-linked-list-cycle-ii
0143-reorder-list
0148-sort-list
0202-happy-number
0321-create-maximum-number
0962-maximum-width-ramp

Sorting

0018-4sum
0047-permutations-ii
0049-group-anagrams
0075-sort-colors
0088-merge-sorted-array
0148-sort-list
0169-majority-element
0179-largest-number
0215-kth-largest-element-in-an-array
0218-the-skyline-problem
0220-contains-duplicate-iii
0229-majority-element-ii
0324-wiggle-sort-ii
0768-max-chunks-to-make-sorted-ii
0769-max-chunks-to-make-sorted
0853-car-fleet
0912-sort-an-array
0975-odd-even-jump

Dynamic Programming

0022-generate-parentheses
0042-trapping-rain-water
0044-wildcard-matching
0045-jump-game-ii
0053-maximum-subarray
0062-unique-paths
0063-unique-paths-ii
0064-minimum-path-sum
0070-climbing-stairs
0072-edit-distance
0085-maximal-rectangle
0087-scramble-string
0091-decode-ways
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0097-interleaving-string
0115-distinct-subsequences
0118-pascals-triangle
0119-pascals-triangle-ii
0122-best-time-to-buy-and-sell-stock-ii
0123-best-time-to-buy-and-sell-stock-iii
0124-binary-tree-maximum-path-sum
0131-palindrome-partitioning
0132-palindrome-partitioning-ii
0139-word-break
0140-word-break-ii
0375-guess-number-higher-or-lower-ii
0376-wiggle-subsequence
0397-integer-replacement
0464-can-i-win
0486-predict-the-winner
0787-cheapest-flights-within-k-stops
0907-sum-of-subarray-minimums
0975-odd-even-jump
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance

Backtracking

0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0037-sudoku-solver
0039-combination-sum
0040-combination-sum-ii
0046-permutations
0047-permutations-ii
0051-n-queens
0052-n-queens-ii
0077-combinations
0089-gray-code
0090-subsets-ii
0093-restore-ip-addresses
0095-unique-binary-search-trees-ii
0126-word-ladder-ii
0131-palindrome-partitioning
0140-word-break-ii

Linked List

0023-merge-k-sorted-lists
0024-swap-nodes-in-pairs
0025-reverse-nodes-in-k-group
0061-rotate-list
0083-remove-duplicates-from-sorted-list
0086-partition-list
0092-reverse-linked-list-ii
0109-convert-sorted-list-to-binary-search-tree
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0138-copy-list-with-random-pointer
0141-linked-list-cycle
0142-linked-list-cycle-ii
0143-reorder-list
0148-sort-list
0203-remove-linked-list-elements
0206-reverse-linked-list
0430-flatten-a-multilevel-doubly-linked-list
0432-all-oone-data-structure
0460-lfu-cache
1472-design-browser-history

Divide and Conquer

0023-merge-k-sorted-lists
0053-maximum-subarray
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0148-sort-list
0169-majority-element
0190-reverse-bits
0191-number-of-1-bits
0215-kth-largest-element-in-an-array
0218-the-skyline-problem
0240-search-a-2d-matrix-ii
0307-range-sum-query-mutable
0315-count-of-smaller-numbers-after-self
0324-wiggle-sort-ii
0327-count-of-range-sum
0493-reverse-pairs
0912-sort-an-array
1649-create-sorted-array-through-instructions

Heap (Priority Queue)

0023-merge-k-sorted-lists
0215-kth-largest-element-in-an-array
0218-the-skyline-problem
0743-network-delay-time
0787-cheapest-flights-within-k-stops
0882-reachable-nodes-in-subdivided-graph
0912-sort-an-array
1368-minimum-cost-to-make-at-least-one-valid-path-in-a-grid

Merge Sort

0023-merge-k-sorted-lists
0148-sort-list
0315-count-of-smaller-numbers-after-self
0327-count-of-range-sum
0493-reverse-pairs
0912-sort-an-array
1649-create-sorted-array-through-instructions

Stack

0042-trapping-rain-water
0085-maximal-rectangle
0094-binary-tree-inorder-traversal
0143-reorder-list
0173-binary-search-tree-iterator
0316-remove-duplicate-letters
0321-create-maximum-number
0402-remove-k-digits
0768-max-chunks-to-make-sorted-ii
0769-max-chunks-to-make-sorted
0853-car-fleet
0901-online-stock-span
0907-sum-of-subarray-minimums
0962-maximum-width-ramp
0975-odd-even-jump
1008-construct-binary-search-tree-from-preorder-traversal
1472-design-browser-history

Monotonic Stack

0042-trapping-rain-water
0085-maximal-rectangle
0316-remove-duplicate-letters
0321-create-maximum-number
0402-remove-k-digits
0768-max-chunks-to-make-sorted-ii
0769-max-chunks-to-make-sorted
0853-car-fleet
0901-online-stock-span
0907-sum-of-subarray-minimums
0962-maximum-width-ramp
0975-odd-even-jump
1008-construct-binary-search-tree-from-preorder-traversal

Greedy

0044-wildcard-matching
0045-jump-game-ii
0122-best-time-to-buy-and-sell-stock-ii
0134-gas-station
0135-candy
0179-largest-number
0316-remove-duplicate-letters
0321-create-maximum-number
0324-wiggle-sort-ii
0330-patching-array
0334-increasing-triplet-subsequence
0376-wiggle-subsequence
0397-integer-replacement
0402-remove-k-digits
0768-max-chunks-to-make-sorted-ii
0769-max-chunks-to-make-sorted

Recursion

0024-swap-nodes-in-pairs
0025-reverse-nodes-in-k-group
0044-wildcard-matching
0050-powx-n
0060-permutation-sequence
0143-reorder-list
0203-remove-linked-list-elements
0206-reverse-linked-list
0231-power-of-two
0486-predict-the-winner

Math

0007-reverse-integer
0009-palindrome-number
0029-divide-two-integers
0050-powx-n
0060-permutation-sequence
0062-unique-paths
0070-climbing-stairs
0089-gray-code
0096-unique-binary-search-trees
0202-happy-number
0231-power-of-two
0375-guess-number-higher-or-lower-ii
0464-can-i-win
0486-predict-the-winner
0810-chalkboard-xor-game

Combinatorics

0062-unique-paths

Matrix

0036-valid-sudoku
0037-sudoku-solver
0063-unique-paths-ii
0064-minimum-path-sum
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0085-maximal-rectangle
0240-search-a-2d-matrix-ii
1368-minimum-cost-to-make-at-least-one-valid-path-in-a-grid

Memoization

0070-climbing-stairs
0139-word-break
0140-word-break-ii
0397-integer-replacement
0464-can-i-win

Sliding Window

0030-substring-with-concatenation-of-all-words
0076-minimum-window-substring
0187-repeated-dna-sequences
0219-contains-duplicate-ii
0220-contains-duplicate-iii

Tree

0094-binary-tree-inorder-traversal
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-binary-search-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0107-binary-tree-level-order-traversal-ii
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0173-binary-search-tree-iterator
0222-count-complete-tree-nodes
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0449-serialize-and-deserialize-bst
0450-delete-node-in-a-bst
0501-find-mode-in-binary-search-tree
0530-minimum-absolute-difference-in-bst
0538-convert-bst-to-greater-tree
0572-subtree-of-another-tree
1008-construct-binary-search-tree-from-preorder-traversal

Binary Tree

0094-binary-tree-inorder-traversal
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-binary-search-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0107-binary-tree-level-order-traversal-ii
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0173-binary-search-tree-iterator
0222-count-complete-tree-nodes
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0449-serialize-and-deserialize-bst
0450-delete-node-in-a-bst
0501-find-mode-in-binary-search-tree
0530-minimum-absolute-difference-in-bst
0538-convert-bst-to-greater-tree
0572-subtree-of-another-tree
1008-construct-binary-search-tree-from-preorder-traversal

Breadth-First Search

0101-symmetric-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0107-binary-tree-level-order-traversal-ii
0111-minimum-depth-of-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0126-word-ladder-ii
0127-word-ladder
0133-clone-graph
0449-serialize-and-deserialize-bst
0530-minimum-absolute-difference-in-bst
0743-network-delay-time
0787-cheapest-flights-within-k-stops
1368-minimum-cost-to-make-at-least-one-valid-path-in-a-grid

Union-Find

0128-longest-consecutive-sequence
0352-data-stream-as-disjoint-intervals

Depth-First Search

0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0099-recover-binary-search-tree
0101-symmetric-tree
0104-maximum-depth-of-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0133-clone-graph
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0430-flatten-a-multilevel-doubly-linked-list
0449-serialize-and-deserialize-bst
0501-find-mode-in-binary-search-tree
0530-minimum-absolute-difference-in-bst
0538-convert-bst-to-greater-tree
0572-subtree-of-another-tree
0743-network-delay-time
0787-cheapest-flights-within-k-stops

Graph Theory

0133-clone-graph
0743-network-delay-time
0787-cheapest-flights-within-k-stops
0882-reachable-nodes-in-subdivided-graph
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1368-minimum-cost-to-make-at-least-one-valid-path-in-a-grid

Trie

0139-word-break
0140-word-break-ii
0208-implement-trie-prefix-tree

Quickselect

0215-kth-largest-element-in-an-array
0324-wiggle-sort-ii

Bit Manipulation

0029-divide-two-integers
0089-gray-code
0090-subsets-ii
0187-repeated-dna-sequences
0190-reverse-bits
0191-number-of-1-bits
0201-bitwise-and-of-numbers-range
0222-count-complete-tree-nodes
0231-power-of-two
0260-single-number-iii
0397-integer-replacement
0464-can-i-win
0810-chalkboard-xor-game

Binary Search Tree

0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0074-search-a-2d-matrix
0081-search-in-rotated-sorted-array-ii
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-binary-search-tree
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0173-binary-search-tree-iterator
0222-count-complete-tree-nodes
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0240-search-a-2d-matrix-ii
0315-count-of-smaller-numbers-after-self
0327-count-of-range-sum
0352-data-stream-as-disjoint-intervals
0449-serialize-and-deserialize-bst
0450-delete-node-in-a-bst
0493-reverse-pairs
0501-find-mode-in-binary-search-tree
0530-minimum-absolute-difference-in-bst
0538-convert-bst-to-greater-tree
1008-construct-binary-search-tree-from-preorder-traversal
1649-create-sorted-array-through-instructions

String Matching

0028-find-the-index-of-the-first-occurrence-in-a-string
0214-shortest-palindrome
0459-repeated-substring-pattern
0572-subtree-of-another-tree
0686-repeated-string-match
0796-rotate-string

Rolling Hash

0187-repeated-dna-sequences
0214-shortest-palindrome

Hash Function

0187-repeated-dna-sequences
0214-shortest-palindrome
0572-subtree-of-another-tree

Design

0173-binary-search-tree-iterator
0208-implement-trie-prefix-tree
0307-range-sum-query-mutable
0352-data-stream-as-disjoint-intervals
0432-all-oone-data-structure
0449-serialize-and-deserialize-bst
0460-lfu-cache
0901-online-stock-span
1472-design-browser-history

Counting

0169-majority-element
0229-majority-element-ii

Data Stream

0352-data-stream-as-disjoint-intervals
0901-online-stock-span
1472-design-browser-history

Ordered Set

0218-the-skyline-problem
0220-contains-duplicate-iii
0315-count-of-smaller-numbers-after-self
0327-count-of-range-sum
0352-data-stream-as-disjoint-intervals
0493-reverse-pairs
0975-odd-even-jump
1649-create-sorted-array-through-instructions

Iterator

0173-binary-search-tree-iterator

Doubly-Linked List

0430-flatten-a-multilevel-doubly-linked-list
0432-all-oone-data-structure
0460-lfu-cache
1472-design-browser-history

Binary Indexed Tree

0218-the-skyline-problem
0307-range-sum-query-mutable
0315-count-of-smaller-numbers-after-self
0327-count-of-range-sum
0493-reverse-pairs
1649-create-sorted-array-through-instructions

Segment Tree

0218-the-skyline-problem
0307-range-sum-query-mutable
0315-count-of-smaller-numbers-after-self
0327-count-of-range-sum
0493-reverse-pairs
1649-create-sorted-array-through-instructions

Sweep Line

0218-the-skyline-problem

Game Theory

0375-guess-number-higher-or-lower-ii
0464-can-i-win
0486-predict-the-winner
0810-chalkboard-xor-game

Bitmask

0464-can-i-win

Brainteaser

0810-chalkboard-xor-game

Bucket Sort

0220-contains-duplicate-iii
0912-sort-an-array

Radix Sort

0912-sort-an-array

Counting Sort

0912-sort-an-array

Shortest Path

0743-network-delay-time
0787-cheapest-flights-within-k-stops
0882-reachable-nodes-in-subdivided-graph
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1368-minimum-cost-to-make-at-least-one-valid-path-in-a-grid