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Leetcode-Solutions

Collection of LeetCode questions to ace the coding interview!

LeetCode Topics

Array

Problem Name Difficulty
0004-median-of-two-sorted-arrays Hard
0011-container-with-most-water Medium
0015-3sum Medium
0016-3sum-closest Medium
0018-4sum Medium
0026-remove-duplicates-from-sorted-array Easy
0031-next-permutation Medium
0033-search-in-rotated-sorted-array Medium
0034-find-first-and-last-position-of-element-in-sorted-array Medium
0039-combination-sum Medium
0040-combination-sum-ii Medium
0042-trapping-rain-water Hard
0045-jump-game-ii Medium
0047-permutations-ii Medium
0049-group-anagrams Medium
0051-n-queens Hard
0053-maximum-subarray Medium
0054-spiral-matrix Medium
0055-jump-game Medium
0056-merge-intervals Medium
0063-unique-paths-ii Medium
0073-set-matrix-zeroes Medium
0074-search-a-2d-matrix Medium
0075-sort-colors Medium
0079-word-search Medium
0081-search-in-rotated-sorted-array-ii Medium
0084-largest-rectangle-in-histogram Hard
0085-maximal-rectangle Hard
0090-subsets-ii Medium
0105-construct-binary-tree-from-preorder-and-inorder-traversal Medium
0106-construct-binary-tree-from-inorder-and-postorder-traversal Medium
0108-convert-sorted-array-to-binary-search-tree Easy
0121-best-time-to-buy-and-sell-stock Easy
0128-longest-consecutive-sequence Medium
0130-surrounded-regions Medium
0134-gas-station Medium
0139-word-break Medium
0140-word-break-ii Hard
0152-maximum-product-subarray Medium
0153-find-minimum-in-rotated-sorted-array Medium
0154-find-minimum-in-rotated-sorted-array-ii Hard
0162-find-peak-element Medium
0169-majority-element Easy
0179-largest-number Medium
0189-rotate-array Medium
0200-number-of-islands Medium
0204-count-primes Medium
0212-word-search-ii Hard
0213-house-robber-ii Medium
0215-kth-largest-element-in-an-array Medium
0221-maximal-square Medium
0239-sliding-window-maximum Hard
0240-search-a-2d-matrix-ii Medium
0300-longest-increasing-subsequence Medium
0303-range-sum-query-immutable Easy
0304-range-sum-query-2d-immutable Medium
0307-range-sum-query-mutable Medium
0312-burst-balloons Hard
0322-coin-change Medium
0334-increasing-triplet-subsequence Medium
0347-top-k-frequent-elements Medium
0354-russian-doll-envelopes Hard
0368-largest-divisible-subset Medium
0410-split-array-largest-sum Hard
0416-partition-equal-subset-sum Medium
0417-pacific-atlantic-water-flow Medium
0421-maximum-xor-of-two-numbers-in-an-array Medium
0435-non-overlapping-intervals Medium
0452-minimum-number-of-arrows-to-burst-balloons Medium
0455-assign-cookies Easy
0486-predict-the-winner Medium
0494-target-sum Medium
0496-next-greater-element-i Easy
0503-next-greater-element-ii Medium
0518-coin-change-ii Medium
0523-continuous-subarray-sum Medium
0525-contiguous-array Medium
0560-subarray-sum-equals-k Medium
0621-task-scheduler Medium
0654-maximum-binary-tree Medium
0673-number-of-longest-increasing-subsequence Medium
0692-top-k-frequent-words Medium
0695-max-area-of-island Medium
0698-partition-to-k-equal-sum-subsets Medium
0704-binary-search Easy
0735-asteroid-collision Medium
0739-daily-temperatures Medium
0740-delete-and-earn Medium
0741-cherry-pickup Hard
0746-min-cost-climbing-stairs Easy
0815-bus-routes Hard
0839-similar-string-groups Hard
0852-peak-index-in-a-mountain-array Medium
0860-lemonade-change Easy
0875-koko-eating-bananas Medium
0879-profitable-schemes Hard
0881-boats-to-save-people Medium
0904-fruit-into-baskets Medium
0905-sort-array-by-parity Easy
0907-sum-of-subarray-minimums Medium
0918-maximum-sum-circular-subarray Medium
0922-sort-array-by-parity-ii Easy
0930-binary-subarrays-with-sum Medium
0962-maximum-width-ramp Medium
0974-subarray-sums-divisible-by-k Medium
0980-unique-paths-iii Hard
0992-subarrays-with-k-different-integers Hard
0994-rotting-oranges Medium
1005-maximize-sum-of-array-after-k-negations Easy
1011-capacity-to-ship-packages-within-d-days Medium
1035-uncrossed-lines Medium
1039-minimum-score-triangulation-of-polygon Medium
1046-last-stone-weight Easy
1091-shortest-path-in-binary-matrix Medium
1094-car-pooling Medium
1095-find-in-mountain-array Hard
1109-corporate-flight-bookings Medium
1200-minimum-absolute-difference Easy
1202-smallest-string-with-swaps Medium
1254-number-of-closed-islands Medium
1293-shortest-path-in-a-grid-with-obstacles-elimination Hard
1306-jump-game-iii Medium
1340-jump-game-v Hard
1345-jump-game-iv Hard
1391-check-if-there-is-a-valid-path-in-a-grid Medium
1431-kids-with-the-greatest-number-of-candies Easy
1463-cherry-pickup-ii Hard
1473-paint-house-iii Hard
1482-minimum-number-of-days-to-make-m-bouquets Medium
1497-check-if-array-pairs-are-divisible-by-k Medium
1514-path-with-maximum-probability Medium
1547-minimum-cost-to-cut-a-stick Hard
1582-special-positions-in-a-binary-matrix Easy
1584-min-cost-to-connect-all-points Medium
1631-path-with-minimum-effort Medium
1642-furthest-building-you-can-reach Medium
1649-create-sorted-array-through-instructions Hard
1710-maximum-units-on-a-truck Easy
1751-maximum-number-of-events-that-can-be-attended-ii Hard
1752-check-if-array-is-sorted-and-rotated Easy
1765-map-of-highest-peak Medium
1773-count-items-matching-a-rule Easy
1877-minimize-maximum-pair-sum-in-array Medium
1937-maximum-number-of-points-with-cost Medium
1980-find-unique-binary-string Medium
2033-minimum-operations-to-make-a-uni-value-grid Medium
2104-sum-of-subarray-ranges Medium
2144-minimum-cost-of-buying-candies-with-discount Easy
2161-partition-array-according-to-given-pivot Medium
2196-create-binary-tree-from-descriptions Medium
2302-count-subarrays-with-score-less-than-k Hard
2341-maximum-number-of-pairs-in-array Easy
2365-task-scheduler-ii Medium
2367-number-of-arithmetic-triplets Easy
2381-shifting-letters-ii Medium
2540-minimum-common-value Easy
2574-left-and-right-sum-differences Easy
2657-find-the-prefix-common-array-of-two-arrays Medium
2845-count-of-interesting-subarrays Medium
2869-minimum-operations-to-collect-elements Easy
2940-find-building-where-alice-and-bob-can-meet Hard
2958-length-of-longest-subarray-with-at-most-k-frequency Medium
3043-find-the-length-of-the-longest-common-prefix Medium
3397-maximum-number-of-distinct-elements-after-operations Medium
3633-earliest-finish-time-for-land-and-water-rides-i Easy
3635-earliest-finish-time-for-land-and-water-rides-ii Medium
3689-maximum-total-subarray-value-i Medium
3740-minimum-distance-between-three-equal-elements-i Easy
3838-weighted-word-mapping Easy

Math

Problem Name Difficulty
0070-climbing-stairs Easy
0089-gray-code Medium
0189-rotate-array Medium
0204-count-primes Medium
0231-power-of-two Easy
0279-perfect-squares Medium
0282-expression-add-operators Hard
0342-power-of-four Easy
0343-integer-break Medium
0368-largest-divisible-subset Medium
0486-predict-the-winner Medium
0523-continuous-subarray-sum Medium
0650-2-keys-keyboard Medium
1317-convert-integer-to-the-sum-of-two-no-zero-integers Easy
2033-minimum-operations-to-make-a-uni-value-grid Medium
3558-number-of-ways-to-assign-edge-weights-i Medium
3751-total-waviness-of-numbers-in-range-i Medium

Dynamic Programming

Problem Name Difficulty
0005-longest-palindromic-substring Medium
0022-generate-parentheses Medium
0042-trapping-rain-water Hard
0045-jump-game-ii Medium
0053-maximum-subarray Medium
0055-jump-game Medium
0063-unique-paths-ii Medium
0070-climbing-stairs Easy
0072-edit-distance Medium
0085-maximal-rectangle Hard
0091-decode-ways Medium
0115-distinct-subsequences Hard
0121-best-time-to-buy-and-sell-stock Easy
0124-binary-tree-maximum-path-sum Hard
0131-palindrome-partitioning Medium
0132-palindrome-partitioning-ii Hard
0139-word-break Medium
0140-word-break-ii Hard
0152-maximum-product-subarray Medium
0213-house-robber-ii Medium
0221-maximal-square Medium
0279-perfect-squares Medium
0300-longest-increasing-subsequence Medium
0312-burst-balloons Hard
0322-coin-change Medium
0337-house-robber-iii Medium
0338-counting-bits Easy
0343-integer-break Medium
0354-russian-doll-envelopes Hard
0368-largest-divisible-subset Medium
0410-split-array-largest-sum Hard
0416-partition-equal-subset-sum Medium
0435-non-overlapping-intervals Medium
0486-predict-the-winner Medium
0494-target-sum Medium
0516-longest-palindromic-subsequence Medium
0518-coin-change-ii Medium
0576-out-of-boundary-paths Medium
0583-delete-operation-for-two-strings Medium
0650-2-keys-keyboard Medium
0673-number-of-longest-increasing-subsequence Medium
0698-partition-to-k-equal-sum-subsets Medium
0740-delete-and-earn Medium
0741-cherry-pickup Hard
0746-min-cost-climbing-stairs Easy
0787-cheapest-flights-within-k-stops Medium
0834-sum-of-distances-in-tree Hard
0847-shortest-path-visiting-all-nodes Hard
0879-profitable-schemes Hard
0907-sum-of-subarray-minimums Medium
0918-maximum-sum-circular-subarray Medium
0968-binary-tree-cameras Hard
1035-uncrossed-lines Medium
1039-minimum-score-triangulation-of-polygon Medium
1092-shortest-common-supersequence Hard
1143-longest-common-subsequence Medium
1312-minimum-insertion-steps-to-make-a-string-palindrome Hard
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance Medium
1340-jump-game-v Hard
1373-maximum-sum-bst-in-binary-tree Hard
1463-cherry-pickup-ii Hard
1473-paint-house-iii Hard
1483-kth-ancestor-of-a-tree-node Hard
1547-minimum-cost-to-cut-a-stick Hard
1751-maximum-number-of-events-that-can-be-attended-ii Hard
1857-largest-color-value-in-a-directed-graph Hard
1871-jump-game-vii Medium
1888-minimum-number-of-flips-to-make-the-binary-string-alternating Medium
1937-maximum-number-of-points-with-cost Medium
1976-number-of-ways-to-arrive-at-destination Medium
3751-total-waviness-of-numbers-in-range-i Medium

Recursion

Problem Name Difficulty
0021-merge-two-sorted-lists Easy
0025-reverse-nodes-in-k-group Hard
0143-reorder-list Medium
0203-remove-linked-list-elements Easy
0206-reverse-linked-list Easy
0231-power-of-two Easy
0342-power-of-four Easy
0486-predict-the-winner Medium

Game Theory

Problem Name Difficulty
0486-predict-the-winner Medium

Backtracking

Problem Name Difficulty
0022-generate-parentheses Medium
0039-combination-sum Medium
0040-combination-sum-ii Medium
0047-permutations-ii Medium
0051-n-queens Hard
0052-n-queens-ii Hard
0077-combinations Medium
0079-word-search Medium
0089-gray-code Medium
0090-subsets-ii Medium
0093-restore-ip-addresses Medium
0131-palindrome-partitioning Medium
0140-word-break-ii Hard
0212-word-search-ii Hard
0257-binary-tree-paths Easy
0282-expression-add-operators Hard
0494-target-sum Medium
0698-partition-to-k-equal-sum-subsets Medium
0797-all-paths-from-source-to-target Medium
0980-unique-paths-iii Hard
1980-find-unique-binary-string Medium

Matrix

Problem Name Difficulty
0054-spiral-matrix Medium
0063-unique-paths-ii Medium
0073-set-matrix-zeroes Medium
0074-search-a-2d-matrix Medium
0079-word-search Medium
0085-maximal-rectangle Hard
0130-surrounded-regions Medium
0200-number-of-islands Medium
0212-word-search-ii Hard
0221-maximal-square Medium
0240-search-a-2d-matrix-ii Medium
0304-range-sum-query-2d-immutable Medium
0417-pacific-atlantic-water-flow Medium
0695-max-area-of-island Medium
0741-cherry-pickup Hard
0980-unique-paths-iii Hard
0994-rotting-oranges Medium
1091-shortest-path-in-binary-matrix Medium
1254-number-of-closed-islands Medium
1293-shortest-path-in-a-grid-with-obstacles-elimination Hard
1391-check-if-there-is-a-valid-path-in-a-grid Medium
1463-cherry-pickup-ii Hard
1582-special-positions-in-a-binary-matrix Easy
1631-path-with-minimum-effort Medium
1765-map-of-highest-peak Medium
1937-maximum-number-of-points-with-cost Medium
2033-minimum-operations-to-make-a-uni-value-grid Medium

Greedy

Problem Name Difficulty
0011-container-with-most-water Medium
0045-jump-game-ii Medium
0055-jump-game Medium
0134-gas-station Medium
0179-largest-number Medium
0334-increasing-triplet-subsequence Medium
0402-remove-k-digits Medium
0410-split-array-largest-sum Hard
0435-non-overlapping-intervals Medium
0452-minimum-number-of-arrows-to-burst-balloons Medium
0455-assign-cookies Easy
0621-task-scheduler Medium
0767-reorganize-string Medium
0860-lemonade-change Easy
0881-boats-to-save-people Medium
1005-maximize-sum-of-array-after-k-negations Easy
1642-furthest-building-you-can-reach Medium
1710-maximum-units-on-a-truck Easy
1877-minimize-maximum-pair-sum-in-array Medium
2144-minimum-cost-of-buying-candies-with-discount Easy
3397-maximum-number-of-distinct-elements-after-operations Medium
3633-earliest-finish-time-for-land-and-water-rides-i Easy
3635-earliest-finish-time-for-land-and-water-rides-ii Medium
3689-maximum-total-subarray-value-i Medium

Breadth-First Search

Problem Name Difficulty
0100-same-tree Easy
0104-maximum-depth-of-binary-tree Easy
0111-minimum-depth-of-binary-tree Easy
0112-path-sum Easy
0117-populating-next-right-pointers-in-each-node-ii Medium
0127-word-ladder Hard
0130-surrounded-regions Medium
0200-number-of-islands Medium
0207-course-schedule Medium
0226-invert-binary-tree Easy
0279-perfect-squares Medium
0297-serialize-and-deserialize-binary-tree Hard
0322-coin-change Medium
0417-pacific-atlantic-water-flow Medium
0433-minimum-genetic-mutation Medium
0547-number-of-provinces Medium
0653-two-sum-iv-input-is-a-bst Easy
0662-maximum-width-of-binary-tree Medium
0684-redundant-connection Medium
0685-redundant-connection-ii Hard
0695-max-area-of-island Medium
0743-network-delay-time Medium
0785-is-graph-bipartite Medium
0787-cheapest-flights-within-k-stops Medium
0797-all-paths-from-source-to-target Medium
0802-find-eventual-safe-states Medium
0815-bus-routes Hard
0839-similar-string-groups Hard
0841-keys-and-rooms Medium
0847-shortest-path-visiting-all-nodes Hard
0863-all-nodes-distance-k-in-binary-tree Medium
0886-possible-bipartition Medium
0987-vertical-order-traversal-of-a-binary-tree Hard
0994-rotting-oranges Medium
1091-shortest-path-in-binary-matrix Medium
1161-maximum-level-sum-of-a-binary-tree Medium
1202-smallest-string-with-swaps Medium
1254-number-of-closed-islands Medium
1293-shortest-path-in-a-grid-with-obstacles-elimination Hard
1306-jump-game-iii Medium
1319-number-of-operations-to-make-network-connected Medium
1345-jump-game-iv Hard
1391-check-if-there-is-a-valid-path-in-a-grid Medium
1483-kth-ancestor-of-a-tree-node Hard
1631-path-with-minimum-effort Medium
1765-map-of-highest-peak Medium
2360-longest-cycle-in-a-graph Hard
2608-shortest-cycle-in-a-graph Hard

String

Problem Name Difficulty
0003-longest-substring-without-repeating-characters Medium
0005-longest-palindromic-substring Medium
0020-valid-parentheses Easy
0022-generate-parentheses Medium
0038-count-and-say Medium
0049-group-anagrams Medium
0072-edit-distance Medium
0076-minimum-window-substring Hard
0079-word-search Medium
0091-decode-ways Medium
0093-restore-ip-addresses Medium
0115-distinct-subsequences Hard
0125-valid-palindrome Easy
0127-word-ladder Hard
0131-palindrome-partitioning Medium
0132-palindrome-partitioning-ii Hard
0139-word-break Medium
0140-word-break-ii Hard
0179-largest-number Medium
0208-implement-trie-prefix-tree Medium
0212-word-search-ii Hard
0257-binary-tree-paths Easy
0282-expression-add-operators Hard
0297-serialize-and-deserialize-binary-tree Hard
0402-remove-k-digits Medium
0424-longest-repeating-character-replacement Medium
0433-minimum-genetic-mutation Medium
0438-find-all-anagrams-in-a-string Medium
0451-sort-characters-by-frequency Medium
0516-longest-palindromic-subsequence Medium
0583-delete-operation-for-two-strings Medium
0692-top-k-frequent-words Medium
0767-reorganize-string Medium
0839-similar-string-groups Hard
1092-shortest-common-supersequence Hard
1143-longest-common-subsequence Medium
1202-smallest-string-with-swaps Medium
1312-minimum-insertion-steps-to-make-a-string-palindrome Hard
1358-number-of-substrings-containing-all-three-characters Medium
1758-minimum-changes-to-make-alternating-binary-string Easy
1773-count-items-matching-a-rule Easy
1857-largest-color-value-in-a-directed-graph Hard
1871-jump-game-vii Medium
1888-minimum-number-of-flips-to-make-the-binary-string-alternating Medium
1930-unique-length-3-palindromic-subsequences Medium
1980-find-unique-binary-string Medium
2381-shifting-letters-ii Medium
3043-find-the-length-of-the-longest-common-prefix Medium
3120-count-the-number-of-special-characters-i Easy
3121-count-the-number-of-special-characters-ii Medium
3597-partition-string Medium
3838-weighted-word-mapping Easy

Binary Search

Problem Name Difficulty
0004-median-of-two-sorted-arrays Hard
0033-search-in-rotated-sorted-array Medium
0034-find-first-and-last-position-of-element-in-sorted-array Medium
0074-search-a-2d-matrix Medium
0081-search-in-rotated-sorted-array-ii Medium
0153-find-minimum-in-rotated-sorted-array Medium
0154-find-minimum-in-rotated-sorted-array-ii Hard
0162-find-peak-element Medium
0240-search-a-2d-matrix-ii Medium
0278-first-bad-version Easy
0300-longest-increasing-subsequence Medium
0354-russian-doll-envelopes Hard
0410-split-array-largest-sum Hard
0704-binary-search Easy
0852-peak-index-in-a-mountain-array Medium
0875-koko-eating-bananas Medium
1011-capacity-to-ship-packages-within-d-days Medium
1095-find-in-mountain-array Hard
1482-minimum-number-of-days-to-make-m-bouquets Medium
1483-kth-ancestor-of-a-tree-node Hard
1631-path-with-minimum-effort Medium
1649-create-sorted-array-through-instructions Hard
1751-maximum-number-of-events-that-can-be-attended-ii Hard
2302-count-subarrays-with-score-less-than-k Hard
2540-minimum-common-value Easy
2940-find-building-where-alice-and-bob-can-meet Hard
3633-earliest-finish-time-for-land-and-water-rides-i Easy
3635-earliest-finish-time-for-land-and-water-rides-ii Medium

Binary Indexed Tree

Problem Name Difficulty
0307-range-sum-query-mutable Medium
0673-number-of-longest-increasing-subsequence Medium
1649-create-sorted-array-through-instructions Hard
2940-find-building-where-alice-and-bob-can-meet Hard

Segment Tree

Problem Name Difficulty
0307-range-sum-query-mutable Medium
0673-number-of-longest-increasing-subsequence Medium
1649-create-sorted-array-through-instructions Hard
2940-find-building-where-alice-and-bob-can-meet Hard

Sorting

Problem Name Difficulty
0015-3sum Medium
0016-3sum-closest Medium
0018-4sum Medium
0047-permutations-ii Medium
0049-group-anagrams Medium
0056-merge-intervals Medium
0075-sort-colors Medium
0148-sort-list Medium
0169-majority-element Easy
0179-largest-number Medium
0215-kth-largest-element-in-an-array Medium
0347-top-k-frequent-elements Medium
0354-russian-doll-envelopes Hard
0368-largest-divisible-subset Medium
0435-non-overlapping-intervals Medium
0451-sort-characters-by-frequency Medium
0452-minimum-number-of-arrows-to-burst-balloons Medium
0455-assign-cookies Easy
0621-task-scheduler Medium
0692-top-k-frequent-words Medium
0767-reorganize-string Medium
0881-boats-to-save-people Medium
0905-sort-array-by-parity Easy
0922-sort-array-by-parity-ii Easy
0987-vertical-order-traversal-of-a-binary-tree Hard
1005-maximize-sum-of-array-after-k-negations Easy
1094-car-pooling Medium
1200-minimum-absolute-difference Easy
1202-smallest-string-with-swaps Medium
1340-jump-game-v Hard
1547-minimum-cost-to-cut-a-stick Hard
1710-maximum-units-on-a-truck Easy
1751-maximum-number-of-events-that-can-be-attended-ii Hard
1877-minimize-maximum-pair-sum-in-array Medium
2033-minimum-operations-to-make-a-uni-value-grid Medium
2144-minimum-cost-of-buying-candies-with-discount Easy
3397-maximum-number-of-distinct-elements-after-operations Medium
3633-earliest-finish-time-for-land-and-water-rides-i Easy
3635-earliest-finish-time-for-land-and-water-rides-ii Medium

Sliding Window

Problem Name Difficulty
0003-longest-substring-without-repeating-characters Medium
0076-minimum-window-substring Hard
0239-sliding-window-maximum Hard
0424-longest-repeating-character-replacement Medium
0438-find-all-anagrams-in-a-string Medium
0904-fruit-into-baskets Medium
0930-binary-subarrays-with-sum Medium
0992-subarrays-with-k-different-integers Hard
1358-number-of-substrings-containing-all-three-characters Medium
1871-jump-game-vii Medium
1888-minimum-number-of-flips-to-make-the-binary-string-alternating Medium
2302-count-subarrays-with-score-less-than-k Hard
2958-length-of-longest-subarray-with-at-most-k-frequency Medium

Hash Table

Problem Name Difficulty
0003-longest-substring-without-repeating-characters Medium
0049-group-anagrams Medium
0073-set-matrix-zeroes Medium
0076-minimum-window-substring Hard
0105-construct-binary-tree-from-preorder-and-inorder-traversal Medium
0106-construct-binary-tree-from-inorder-and-postorder-traversal Medium
0127-word-ladder Hard
0128-longest-consecutive-sequence Medium
0138-copy-list-with-random-pointer Medium
0139-word-break Medium
0140-word-break-ii Hard
0141-linked-list-cycle Easy
0142-linked-list-cycle-ii Medium
0160-intersection-of-two-linked-lists Easy
0169-majority-element Easy
0208-implement-trie-prefix-tree Medium
0347-top-k-frequent-elements Medium
0421-maximum-xor-of-two-numbers-in-an-array Medium
0424-longest-repeating-character-replacement Medium
0433-minimum-genetic-mutation Medium
0438-find-all-anagrams-in-a-string Medium
0451-sort-characters-by-frequency Medium
0460-lfu-cache Hard
0496-next-greater-element-i Easy
0523-continuous-subarray-sum Medium
0525-contiguous-array Medium
0560-subarray-sum-equals-k Medium
0621-task-scheduler Medium
0653-two-sum-iv-input-is-a-bst Easy
0692-top-k-frequent-words Medium
0740-delete-and-earn Medium
0767-reorganize-string Medium
0815-bus-routes Hard
0839-similar-string-groups Hard
0863-all-nodes-distance-k-in-binary-tree Medium
0904-fruit-into-baskets Medium
0930-binary-subarrays-with-sum Medium
0974-subarray-sums-divisible-by-k Medium
0987-vertical-order-traversal-of-a-binary-tree Hard
0992-subarrays-with-k-different-integers Hard
1202-smallest-string-with-swaps Medium
1345-jump-game-iv Hard
1358-number-of-substrings-containing-all-three-characters Medium
1497-check-if-array-pairs-are-divisible-by-k Medium
1857-largest-color-value-in-a-directed-graph Hard
1930-unique-length-3-palindromic-subsequences Medium
1980-find-unique-binary-string Medium
2196-create-binary-tree-from-descriptions Medium
2341-maximum-number-of-pairs-in-array Easy
2365-task-scheduler-ii Medium
2367-number-of-arithmetic-triplets Easy
2540-minimum-common-value Easy
2657-find-the-prefix-common-array-of-two-arrays Medium
2845-count-of-interesting-subarrays Medium
2869-minimum-operations-to-collect-elements Easy
2958-length-of-longest-subarray-with-at-most-k-frequency Medium
3043-find-the-length-of-the-longest-common-prefix Medium
3120-count-the-number-of-special-characters-i Easy
3121-count-the-number-of-special-characters-ii Medium
3597-partition-string Medium
3740-minimum-distance-between-three-equal-elements-i Easy

Tree

Problem Name Difficulty
0094-binary-tree-inorder-traversal Easy
0098-validate-binary-search-tree Medium
0099-recover-binary-search-tree Medium
0100-same-tree Easy
0104-maximum-depth-of-binary-tree Easy
0105-construct-binary-tree-from-preorder-and-inorder-traversal Medium
0106-construct-binary-tree-from-inorder-and-postorder-traversal Medium
0108-convert-sorted-array-to-binary-search-tree Easy
0110-balanced-binary-tree Easy
0111-minimum-depth-of-binary-tree Easy
0112-path-sum Easy
0114-flatten-binary-tree-to-linked-list Medium
0117-populating-next-right-pointers-in-each-node-ii Medium
0124-binary-tree-maximum-path-sum Hard
0144-binary-tree-preorder-traversal Easy
0226-invert-binary-tree Easy
0230-kth-smallest-element-in-a-bst Medium
0235-lowest-common-ancestor-of-a-binary-search-tree Medium
0236-lowest-common-ancestor-of-a-binary-tree Medium
0257-binary-tree-paths Easy
0297-serialize-and-deserialize-binary-tree Hard
0337-house-robber-iii Medium
0437-path-sum-iii Medium
0450-delete-node-in-a-bst Medium
0543-diameter-of-binary-tree Easy
0653-two-sum-iv-input-is-a-bst Easy
0654-maximum-binary-tree Medium
0662-maximum-width-of-binary-tree Medium
0700-search-in-a-binary-search-tree Easy
0701-insert-into-a-binary-search-tree Medium
0834-sum-of-distances-in-tree Hard
0863-all-nodes-distance-k-in-binary-tree Medium
0968-binary-tree-cameras Hard
0987-vertical-order-traversal-of-a-binary-tree Hard
1038-binary-search-tree-to-greater-sum-tree Medium
1161-maximum-level-sum-of-a-binary-tree Medium
1373-maximum-sum-bst-in-binary-tree Hard
1483-kth-ancestor-of-a-tree-node Hard
2196-create-binary-tree-from-descriptions Medium
3558-number-of-ways-to-assign-edge-weights-i Medium

Depth-First Search

Problem Name Difficulty
0079-word-search Medium
0094-binary-tree-inorder-traversal Easy
0098-validate-binary-search-tree Medium
0099-recover-binary-search-tree Medium
0100-same-tree Easy
0104-maximum-depth-of-binary-tree Easy
0110-balanced-binary-tree Easy
0111-minimum-depth-of-binary-tree Easy
0112-path-sum Easy
0114-flatten-binary-tree-to-linked-list Medium
0117-populating-next-right-pointers-in-each-node-ii Medium
0124-binary-tree-maximum-path-sum Hard
0130-surrounded-regions Medium
0144-binary-tree-preorder-traversal Easy
0200-number-of-islands Medium
0207-course-schedule Medium
0226-invert-binary-tree Easy
0230-kth-smallest-element-in-a-bst Medium
0235-lowest-common-ancestor-of-a-binary-search-tree Medium
0236-lowest-common-ancestor-of-a-binary-tree Medium
0257-binary-tree-paths Easy
0297-serialize-and-deserialize-binary-tree Hard
0337-house-robber-iii Medium
0417-pacific-atlantic-water-flow Medium
0430-flatten-a-multilevel-doubly-linked-list Medium
0437-path-sum-iii Medium
0543-diameter-of-binary-tree Easy
0547-number-of-provinces Medium
0653-two-sum-iv-input-is-a-bst Easy
0662-maximum-width-of-binary-tree Medium
0684-redundant-connection Medium
0685-redundant-connection-ii Hard
0695-max-area-of-island Medium
0743-network-delay-time Medium
0785-is-graph-bipartite Medium
0787-cheapest-flights-within-k-stops Medium
0797-all-paths-from-source-to-target Medium
0802-find-eventual-safe-states Medium
0834-sum-of-distances-in-tree Hard
0839-similar-string-groups Hard
0841-keys-and-rooms Medium
0863-all-nodes-distance-k-in-binary-tree Medium
0886-possible-bipartition Medium
0968-binary-tree-cameras Hard
0987-vertical-order-traversal-of-a-binary-tree Hard
1038-binary-search-tree-to-greater-sum-tree Medium
1161-maximum-level-sum-of-a-binary-tree Medium
1202-smallest-string-with-swaps Medium
1254-number-of-closed-islands Medium
1306-jump-game-iii Medium
1319-number-of-operations-to-make-network-connected Medium
1373-maximum-sum-bst-in-binary-tree Hard
1391-check-if-there-is-a-valid-path-in-a-grid Medium
1483-kth-ancestor-of-a-tree-node Hard
1631-path-with-minimum-effort Medium
2360-longest-cycle-in-a-graph Hard
3558-number-of-ways-to-assign-edge-weights-i Medium

Graph Theory

Problem Name Difficulty
0207-course-schedule Medium
0547-number-of-provinces Medium
0684-redundant-connection Medium
0685-redundant-connection-ii Hard
0743-network-delay-time Medium
0785-is-graph-bipartite Medium
0787-cheapest-flights-within-k-stops Medium
0797-all-paths-from-source-to-target Medium
0802-find-eventual-safe-states Medium
0834-sum-of-distances-in-tree Hard
0841-keys-and-rooms Medium
0847-shortest-path-visiting-all-nodes Hard
0886-possible-bipartition Medium
1319-number-of-operations-to-make-network-connected Medium
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance Medium
1514-path-with-maximum-probability Medium
1557-minimum-number-of-vertices-to-reach-all-nodes Medium
1584-min-cost-to-connect-all-points Medium
1857-largest-color-value-in-a-directed-graph Hard
1976-number-of-ways-to-arrive-at-destination Medium
2360-longest-cycle-in-a-graph Hard
2608-shortest-cycle-in-a-graph Hard

Divide and Conquer

Problem Name Difficulty
0004-median-of-two-sorted-arrays Hard
0023-merge-k-sorted-lists Hard
0053-maximum-subarray Medium
0105-construct-binary-tree-from-preorder-and-inorder-traversal Medium
0106-construct-binary-tree-from-inorder-and-postorder-traversal Medium
0108-convert-sorted-array-to-binary-search-tree Easy
0148-sort-list Medium
0169-majority-element Easy
0215-kth-largest-element-in-an-array Medium
0240-search-a-2d-matrix-ii Medium
0307-range-sum-query-mutable Medium
0347-top-k-frequent-elements Medium
0654-maximum-binary-tree Medium
0918-maximum-sum-circular-subarray Medium
1649-create-sorted-array-through-instructions Hard

Binary Tree

Problem Name Difficulty
0094-binary-tree-inorder-traversal Easy
0098-validate-binary-search-tree Medium
0099-recover-binary-search-tree Medium
0100-same-tree Easy
0104-maximum-depth-of-binary-tree Easy
0105-construct-binary-tree-from-preorder-and-inorder-traversal Medium
0106-construct-binary-tree-from-inorder-and-postorder-traversal Medium
0108-convert-sorted-array-to-binary-search-tree Easy
0110-balanced-binary-tree Easy
0111-minimum-depth-of-binary-tree Easy
0112-path-sum Easy
0114-flatten-binary-tree-to-linked-list Medium
0117-populating-next-right-pointers-in-each-node-ii Medium
0124-binary-tree-maximum-path-sum Hard
0144-binary-tree-preorder-traversal Easy
0226-invert-binary-tree Easy
0230-kth-smallest-element-in-a-bst Medium
0235-lowest-common-ancestor-of-a-binary-search-tree Medium
0236-lowest-common-ancestor-of-a-binary-tree Medium
0257-binary-tree-paths Easy
0297-serialize-and-deserialize-binary-tree Hard
0337-house-robber-iii Medium
0437-path-sum-iii Medium
0450-delete-node-in-a-bst Medium
0543-diameter-of-binary-tree Easy
0653-two-sum-iv-input-is-a-bst Easy
0654-maximum-binary-tree Medium
0662-maximum-width-of-binary-tree Medium
0700-search-in-a-binary-search-tree Easy
0701-insert-into-a-binary-search-tree Medium
0863-all-nodes-distance-k-in-binary-tree Medium
0968-binary-tree-cameras Hard
0987-vertical-order-traversal-of-a-binary-tree Hard
1038-binary-search-tree-to-greater-sum-tree Medium
1161-maximum-level-sum-of-a-binary-tree Medium
1373-maximum-sum-bst-in-binary-tree Hard
2196-create-binary-tree-from-descriptions Medium

Bit Manipulation

Problem Name Difficulty
0089-gray-code Medium
0090-subsets-ii Medium
0231-power-of-two Easy
0338-counting-bits Easy
0342-power-of-four Easy
0421-maximum-xor-of-two-numbers-in-an-array Medium
0698-partition-to-k-equal-sum-subsets Medium
0847-shortest-path-visiting-all-nodes Hard
0980-unique-paths-iii Hard
1483-kth-ancestor-of-a-tree-node Hard
1930-unique-length-3-palindromic-subsequences Medium
2657-find-the-prefix-common-array-of-two-arrays Medium
2869-minimum-operations-to-collect-elements Easy

Design

Problem Name Difficulty
0208-implement-trie-prefix-tree Medium
0297-serialize-and-deserialize-binary-tree Hard
0303-range-sum-query-immutable Easy
0304-range-sum-query-2d-immutable Medium
0307-range-sum-query-mutable Medium
0460-lfu-cache Hard
1483-kth-ancestor-of-a-tree-node Hard

Binary Search Tree

Problem Name Difficulty
0098-validate-binary-search-tree Medium
0099-recover-binary-search-tree Medium
0108-convert-sorted-array-to-binary-search-tree Easy
0230-kth-smallest-element-in-a-bst Medium
0235-lowest-common-ancestor-of-a-binary-search-tree Medium
0450-delete-node-in-a-bst Medium
0653-two-sum-iv-input-is-a-bst Easy
0700-search-in-a-binary-search-tree Easy
0701-insert-into-a-binary-search-tree Medium
1038-binary-search-tree-to-greater-sum-tree Medium
1373-maximum-sum-bst-in-binary-tree Hard

Two Pointers

Problem Name Difficulty
0005-longest-palindromic-substring Medium
0011-container-with-most-water Medium
0015-3sum Medium
0016-3sum-closest Medium
0018-4sum Medium
0026-remove-duplicates-from-sorted-array Easy
0031-next-permutation Medium
0042-trapping-rain-water Hard
0061-rotate-list Medium
0075-sort-colors Medium
0125-valid-palindrome Easy
0141-linked-list-cycle Easy
0142-linked-list-cycle-ii Medium
0143-reorder-list Medium
0148-sort-list Medium
0160-intersection-of-two-linked-lists Easy
0189-rotate-array Medium
0455-assign-cookies Easy
0653-two-sum-iv-input-is-a-bst Easy
0876-middle-of-the-linked-list Easy
0881-boats-to-save-people Medium
0905-sort-array-by-parity Easy
0922-sort-array-by-parity-ii Easy
0962-maximum-width-ramp Medium
1877-minimize-maximum-pair-sum-in-array Medium
2130-maximum-twin-sum-of-a-linked-list Medium
2161-partition-array-according-to-given-pivot Medium
2367-number-of-arithmetic-triplets Easy
2540-minimum-common-value Easy
3633-earliest-finish-time-for-land-and-water-rides-i Easy
3635-earliest-finish-time-for-land-and-water-rides-ii Medium

Prefix Sum

Problem Name Difficulty
0303-range-sum-query-immutable Easy
0304-range-sum-query-2d-immutable Medium
0410-split-array-largest-sum Hard
0523-continuous-subarray-sum Medium
0525-contiguous-array Medium
0560-subarray-sum-equals-k Medium
0930-binary-subarrays-with-sum Medium
0974-subarray-sums-divisible-by-k Medium
1094-car-pooling Medium
1109-corporate-flight-bookings Medium
1871-jump-game-vii Medium
1930-unique-length-3-palindromic-subsequences Medium
2302-count-subarrays-with-score-less-than-k Hard
2381-shifting-letters-ii Medium
2574-left-and-right-sum-differences Easy
2845-count-of-interesting-subarrays Medium

Linked List

Problem Name Difficulty
0021-merge-two-sorted-lists Easy
0023-merge-k-sorted-lists Hard
0025-reverse-nodes-in-k-group Hard
0061-rotate-list Medium
0092-reverse-linked-list-ii Medium
0114-flatten-binary-tree-to-linked-list Medium
0117-populating-next-right-pointers-in-each-node-ii Medium
0138-copy-list-with-random-pointer Medium
0141-linked-list-cycle Easy
0142-linked-list-cycle-ii Medium
0143-reorder-list Medium
0148-sort-list Medium
0160-intersection-of-two-linked-lists Easy
0203-remove-linked-list-elements Easy
0206-reverse-linked-list Easy
0430-flatten-a-multilevel-doubly-linked-list Medium
0460-lfu-cache Hard
0876-middle-of-the-linked-list Easy
1669-merge-in-between-linked-lists Medium
2130-maximum-twin-sum-of-a-linked-list Medium

Stack

Problem Name Difficulty
0020-valid-parentheses Easy
0042-trapping-rain-water Hard
0084-largest-rectangle-in-histogram Hard
0085-maximal-rectangle Hard
0094-binary-tree-inorder-traversal Easy
0114-flatten-binary-tree-to-linked-list Medium
0143-reorder-list Medium
0144-binary-tree-preorder-traversal Easy
0402-remove-k-digits Medium
0496-next-greater-element-i Easy
0503-next-greater-element-ii Medium
0654-maximum-binary-tree Medium
0735-asteroid-collision Medium
0739-daily-temperatures Medium
0907-sum-of-subarray-minimums Medium
0962-maximum-width-ramp Medium
2104-sum-of-subarray-ranges Medium
2130-maximum-twin-sum-of-a-linked-list Medium
2940-find-building-where-alice-and-bob-can-meet Hard

Trie

Problem Name Difficulty
0139-word-break Medium
0140-word-break-ii Hard
0208-implement-trie-prefix-tree Medium
0212-word-search-ii Hard
0421-maximum-xor-of-two-numbers-in-an-array Medium
0692-top-k-frequent-words Medium
3043-find-the-length-of-the-longest-common-prefix Medium
3597-partition-string Medium

Bitmask

Problem Name Difficulty
0698-partition-to-k-equal-sum-subsets Medium
0847-shortest-path-visiting-all-nodes Hard

Union-Find

Problem Name Difficulty
0128-longest-consecutive-sequence Medium
0130-surrounded-regions Medium
0200-number-of-islands Medium
0547-number-of-provinces Medium
0684-redundant-connection Medium
0685-redundant-connection-ii Hard
0695-max-area-of-island Medium
0785-is-graph-bipartite Medium
0839-similar-string-groups Hard
0886-possible-bipartition Medium
1202-smallest-string-with-swaps Medium
1254-number-of-closed-islands Medium
1319-number-of-operations-to-make-network-connected Medium
1391-check-if-there-is-a-valid-path-in-a-grid Medium
1584-min-cost-to-connect-all-points Medium
1631-path-with-minimum-effort Medium

Topological Sort

Problem Name Difficulty
0207-course-schedule Medium
0802-find-eventual-safe-states Medium
1857-largest-color-value-in-a-directed-graph Hard
1976-number-of-ways-to-arrive-at-destination Medium
2360-longest-cycle-in-a-graph Hard

Heap (Priority Queue)

Problem Name Difficulty
0023-merge-k-sorted-lists Hard
0215-kth-largest-element-in-an-array Medium
0239-sliding-window-maximum Hard
0347-top-k-frequent-elements Medium
0451-sort-characters-by-frequency Medium
0621-task-scheduler Medium
0692-top-k-frequent-words Medium
0743-network-delay-time Medium
0767-reorganize-string Medium
0787-cheapest-flights-within-k-stops Medium
1046-last-stone-weight Easy
1094-car-pooling Medium
1514-path-with-maximum-probability Medium
1631-path-with-minimum-effort Medium
1642-furthest-building-you-can-reach Medium
2940-find-building-where-alice-and-bob-can-meet Hard

Shortest Path

Problem Name Difficulty
0743-network-delay-time Medium
0787-cheapest-flights-within-k-stops Medium
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance Medium
1514-path-with-maximum-probability Medium
1976-number-of-ways-to-arrive-at-destination Medium

Interactive

Problem Name Difficulty
0278-first-bad-version Easy
1095-find-in-mountain-array Hard

Merge Sort

Problem Name Difficulty
0023-merge-k-sorted-lists Hard
0148-sort-list Medium
1649-create-sorted-array-through-instructions Hard

Ordered Set

Problem Name Difficulty
1649-create-sorted-array-through-instructions Hard

Monotonic Stack

Problem Name Difficulty
0042-trapping-rain-water Hard
0084-largest-rectangle-in-histogram Hard
0085-maximal-rectangle Hard
0402-remove-k-digits Medium
0496-next-greater-element-i Easy
0503-next-greater-element-ii Medium
0654-maximum-binary-tree Medium
0739-daily-temperatures Medium
0907-sum-of-subarray-minimums Medium
0962-maximum-width-ramp Medium
2104-sum-of-subarray-ranges Medium
2940-find-building-where-alice-and-bob-can-meet Hard

Quickselect

Problem Name Difficulty
0215-kth-largest-element-in-an-array Medium
0347-top-k-frequent-elements Medium

Queue

Problem Name Difficulty
0239-sliding-window-maximum Hard
0918-maximum-sum-circular-subarray Medium

Monotonic Queue

Problem Name Difficulty
0239-sliding-window-maximum Hard
0918-maximum-sum-circular-subarray Medium

Counting

Problem Name Difficulty
0169-majority-element Easy
0347-top-k-frequent-elements Medium
0451-sort-characters-by-frequency Medium
0621-task-scheduler Medium
0692-top-k-frequent-words Medium
0767-reorganize-string Medium
0992-subarrays-with-k-different-integers Hard
1497-check-if-array-pairs-are-divisible-by-k Medium
1857-largest-color-value-in-a-directed-graph Hard
2341-maximum-number-of-pairs-in-array Easy

Simulation

Problem Name Difficulty
0054-spiral-matrix Medium
0735-asteroid-collision Medium
1094-car-pooling Medium
2161-partition-array-according-to-given-pivot Medium
2365-task-scheduler-ii Medium
3597-partition-string Medium
3838-weighted-word-mapping Easy

Memoization

Problem Name Difficulty
0070-climbing-stairs Easy
0139-word-break Medium
0140-word-break-ii Hard
0698-partition-to-k-equal-sum-subsets Medium
1857-largest-color-value-in-a-directed-graph Hard

Minimum Spanning Tree

Problem Name Difficulty
1584-min-cost-to-connect-all-points Medium

Bucket Sort

Problem Name Difficulty
0347-top-k-frequent-elements Medium
0451-sort-characters-by-frequency Medium
0692-top-k-frequent-words Medium

Database

Problem Name Difficulty
0175-combine-two-tables Easy
0176-second-highest-salary Medium
0181-employees-earning-more-than-their-managers Easy
0182-duplicate-emails Easy
0183-customers-who-never-order Easy
0197-rising-temperature Easy
0570-managers-with-at-least-5-direct-reports Medium
0577-employee-bonus Easy
0586-customer-placing-the-largest-number-of-orders Easy
0595-big-countries Easy
0596-classes-with-at-least-5-students Easy
0619-biggest-single-number Easy
0620-not-boring-movies Easy
0627-swap-sex-of-employees Easy
1050-actors-and-directors-who-cooperated-at-least-three-times Easy
1068-product-sales-analysis-i Easy
1075-project-employees-i Easy
1148-article-views-i Easy
1174-immediate-food-delivery-ii Medium
1211-queries-quality-and-percentage Easy
1251-average-selling-price Easy
1484-group-sold-products-by-the-date Easy
1661-average-time-of-process-per-machine Easy
1683-invalid-tweets Easy
1729-find-followers-count Easy
1873-calculate-special-bonus Easy
1934-confirmation-rate Medium

Doubly-Linked List

Problem Name Difficulty
0430-flatten-a-multilevel-doubly-linked-list Medium
0460-lfu-cache Hard

Enumeration

Problem Name Difficulty
0204-count-primes Medium
2367-number-of-arithmetic-triplets Easy
3751-total-waviness-of-numbers-in-range-i Medium

Number Theory

Problem Name Difficulty
0204-count-primes Medium

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Collection of LeetCode questions to ace the coding interview! - Created using [LeetHub-3.0](https://github.com/raphaelheinz/LeetHub-3.0)

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