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Leetcode

Collection of LeetCode questions - Created using LeetHub-3.0

LeetCode Topics

String

Problem Name Difficulty
0005-longest-palindromic-substring Medium
0013-roman-to-integer Easy
0017-letter-combinations-of-a-phone-number Medium
0022-generate-parentheses Medium
0032-longest-valid-parentheses Hard
0038-count-and-say Medium
0058-length-of-last-word Easy
0067-add-binary Easy
0071-simplify-path Medium
0072-edit-distance Medium
0091-decode-ways Medium
0093-restore-ip-addresses Medium
0127-word-ladder Hard
0131-palindrome-partitioning Medium
0139-word-break Medium
0208-implement-trie-prefix-tree Medium
0211-design-add-and-search-words-data-structure Medium
0241-different-ways-to-add-parentheses Medium
0290-word-pattern Easy
0297-serialize-and-deserialize-binary-tree Hard
0301-remove-invalid-parentheses Hard
0394-decode-string Medium
0474-ones-and-zeroes Medium
0583-delete-operation-for-two-strings Medium
0712-minimum-ascii-delete-sum-for-two-strings Medium
0721-accounts-merge Medium
0752-open-the-lock Medium
0784-letter-case-permutation Medium
0842-split-array-into-fibonacci-sequence Medium
0921-minimum-add-to-make-parentheses-valid Medium
0990-satisfiability-of-equality-equations Medium
1047-remove-all-adjacent-duplicates-in-string Easy
1202-smallest-string-with-swaps Medium
1422-maximum-score-after-splitting-a-string Easy

Stack

Problem Name Difficulty
0032-longest-valid-parentheses Hard
0071-simplify-path Medium
0094-binary-tree-inorder-traversal Easy
0114-flatten-binary-tree-to-linked-list Medium
0144-binary-tree-preorder-traversal Easy
0145-binary-tree-postorder-traversal Easy
0394-decode-string Medium
0921-minimum-add-to-make-parentheses-valid Medium
1047-remove-all-adjacent-duplicates-in-string Easy

Recursion

Problem Name Difficulty
0050-powx-n Medium
0203-remove-linked-list-elements Easy
0241-different-ways-to-add-parentheses Medium
0394-decode-string Medium
0509-fibonacci-number Easy

Dynamic Programming

Problem Name Difficulty
0005-longest-palindromic-substring Medium
0022-generate-parentheses Medium
0032-longest-valid-parentheses Hard
0062-unique-paths Medium
0063-unique-paths-ii Medium
0070-climbing-stairs Easy
0072-edit-distance Medium
0091-decode-ways Medium
0118-pascals-triangle Easy
0131-palindrome-partitioning Medium
0139-word-break Medium
0198-house-robber Medium
0213-house-robber-ii Medium
0241-different-ways-to-add-parentheses Medium
0322-coin-change Medium
0343-integer-break Medium
0474-ones-and-zeroes Medium
0509-fibonacci-number Easy
0518-coin-change-ii Medium
0526-beautiful-arrangement Medium
0583-delete-operation-for-two-strings Medium
0698-partition-to-k-equal-sum-subsets Medium
0712-minimum-ascii-delete-sum-for-two-strings Medium
0746-min-cost-climbing-stairs Easy
1049-last-stone-weight-ii Medium
1137-n-th-tribonacci-number Easy
1425-constrained-subsequence-sum Hard
1696-jump-game-vi Medium

Backtracking

Problem Name Difficulty
0017-letter-combinations-of-a-phone-number Medium
0022-generate-parentheses Medium
0039-combination-sum Medium
0040-combination-sum-ii Medium
0046-permutations Medium
0047-permutations-ii Medium
0051-n-queens Hard
0052-n-queens-ii Hard
0077-combinations Medium
0078-subsets Medium
0090-subsets-ii Medium
0093-restore-ip-addresses Medium
0113-path-sum-ii Medium
0131-palindrome-partitioning Medium
0216-combination-sum-iii Medium
0301-remove-invalid-parentheses Hard
0526-beautiful-arrangement Medium
0698-partition-to-k-equal-sum-subsets Medium
0784-letter-case-permutation Medium
0797-all-paths-from-source-to-target Medium
0842-split-array-into-fibonacci-sequence Medium

Breadth-First Search

Problem Name Difficulty
0100-same-tree Easy
0101-symmetric-tree Easy
0102-binary-tree-level-order-traversal Medium
0103-binary-tree-zigzag-level-order-traversal Medium
0104-maximum-depth-of-binary-tree Easy
0111-minimum-depth-of-binary-tree Easy
0112-path-sum Easy
0116-populating-next-right-pointers-in-each-node Medium
0127-word-ladder Hard
0133-clone-graph Medium
0199-binary-tree-right-side-view Medium
0207-course-schedule Medium
0210-course-schedule-ii Medium
0226-invert-binary-tree Easy
0297-serialize-and-deserialize-binary-tree Hard
0301-remove-invalid-parentheses Hard
0310-minimum-height-trees Medium
0322-coin-change Medium
0417-pacific-atlantic-water-flow Medium
0637-average-of-levels-in-binary-tree Easy
0684-redundant-connection Medium
0721-accounts-merge Medium
0752-open-the-lock Medium
0797-all-paths-from-source-to-target Medium
0909-snakes-and-ladders Medium
0987-vertical-order-traversal-of-a-binary-tree Hard
0994-rotting-oranges Medium
1091-shortest-path-in-binary-matrix Medium
1202-smallest-string-with-swaps Medium
1203-sort-items-by-groups-respecting-dependencies Hard

Math

Problem Name Difficulty
0009-palindrome-number Easy
0013-roman-to-integer Easy
0029-divide-two-integers Medium
0050-powx-n Medium
0062-unique-paths Medium
0066-plus-one Easy
0067-add-binary Easy
0070-climbing-stairs Easy
0241-different-ways-to-add-parentheses Medium
0292-nim-game Easy
0343-integer-break Medium
0367-valid-perfect-square Easy
0509-fibonacci-number Easy
1137-n-th-tribonacci-number Easy
1588-sum-of-all-odd-length-subarrays Easy

Memoization

Problem Name Difficulty
0070-climbing-stairs Easy
0139-word-break Medium
0241-different-ways-to-add-parentheses Medium
0509-fibonacci-number Easy
0698-partition-to-k-equal-sum-subsets Medium
1137-n-th-tribonacci-number Easy

Greedy

Problem Name Difficulty
0921-minimum-add-to-make-parentheses-valid Medium

Array

Problem Name Difficulty
0026-remove-duplicates-from-sorted-array Easy
0027-remove-element Easy
0031-next-permutation Medium
0034-find-first-and-last-position-of-element-in-sorted-array Medium
0035-search-insert-position Easy
0039-combination-sum Medium
0040-combination-sum-ii Medium
0046-permutations Medium
0047-permutations-ii Medium
0051-n-queens Hard
0063-unique-paths-ii Medium
0066-plus-one Easy
0078-subsets Medium
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
0118-pascals-triangle Easy
0139-word-break Medium
0169-majority-element Easy
0198-house-robber Medium
0213-house-robber-ii Medium
0216-combination-sum-iii Medium
0217-contains-duplicate Easy
0219-contains-duplicate-ii Easy
0229-majority-element-ii Medium
0239-sliding-window-maximum Hard
0304-range-sum-query-2d-immutable Medium
0322-coin-change Medium
0417-pacific-atlantic-water-flow Medium
0474-ones-and-zeroes Medium
0518-coin-change-ii Medium
0526-beautiful-arrangement Medium
0641-design-circular-deque Medium
0698-partition-to-k-equal-sum-subsets Medium
0721-accounts-merge Medium
0746-min-cost-climbing-stairs Easy
0752-open-the-lock Medium
0862-shortest-subarray-with-sum-at-least-k Hard
0904-fruit-into-baskets Medium
0909-snakes-and-ladders Medium
0990-satisfiability-of-equality-equations Medium
0994-rotting-oranges Medium
1046-last-stone-weight Easy
1049-last-stone-weight-ii Medium
1091-shortest-path-in-binary-matrix Medium
1202-smallest-string-with-swaps Medium
1413-minimum-value-to-get-positive-step-by-step-sum Easy
1425-constrained-subsequence-sum Hard
1480-running-sum-of-1d-array Easy
1588-sum-of-all-odd-length-subarrays Easy
1696-jump-game-vi Medium
1732-find-the-highest-altitude Easy
2073-time-needed-to-buy-tickets Easy

Queue

Problem Name Difficulty
0239-sliding-window-maximum Hard
0641-design-circular-deque Medium
0862-shortest-subarray-with-sum-at-least-k Hard
1425-constrained-subsequence-sum Hard
1696-jump-game-vi Medium
2073-time-needed-to-buy-tickets Easy

Sliding Window

Problem Name Difficulty
0219-contains-duplicate-ii Easy
0239-sliding-window-maximum Hard
0862-shortest-subarray-with-sum-at-least-k Hard
0904-fruit-into-baskets Medium
1425-constrained-subsequence-sum Hard

Heap (Priority Queue)

Problem Name Difficulty
0239-sliding-window-maximum Hard
0703-kth-largest-element-in-a-stream Easy
0862-shortest-subarray-with-sum-at-least-k Hard
1046-last-stone-weight Easy
1425-constrained-subsequence-sum Hard
1696-jump-game-vi Medium

Monotonic Queue

Problem Name Difficulty
0239-sliding-window-maximum Hard
0862-shortest-subarray-with-sum-at-least-k Hard
1425-constrained-subsequence-sum Hard
1696-jump-game-vi Medium

Binary Search

Problem Name Difficulty
0034-find-first-and-last-position-of-element-in-sorted-array Medium
0035-search-insert-position Easy
0367-valid-perfect-square Easy
0862-shortest-subarray-with-sum-at-least-k Hard

Prefix Sum

Problem Name Difficulty
0304-range-sum-query-2d-immutable Medium
0862-shortest-subarray-with-sum-at-least-k Hard
1413-minimum-value-to-get-positive-step-by-step-sum Easy
1422-maximum-score-after-splitting-a-string Easy
1480-running-sum-of-1d-array Easy
1588-sum-of-all-odd-length-subarrays Easy
1732-find-the-highest-altitude Easy

Linked List

Problem Name Difficulty
0114-flatten-binary-tree-to-linked-list Medium
0116-populating-next-right-pointers-in-each-node Medium
0138-copy-list-with-random-pointer Medium
0203-remove-linked-list-elements Easy
0641-design-circular-deque Medium

Design

Problem Name Difficulty
0208-implement-trie-prefix-tree Medium
0211-design-add-and-search-words-data-structure Medium
0297-serialize-and-deserialize-binary-tree Hard
0304-range-sum-query-2d-immutable Medium
0641-design-circular-deque Medium
0703-kth-largest-element-in-a-stream Easy

Tree

Problem Name Difficulty
0094-binary-tree-inorder-traversal Easy
0098-validate-binary-search-tree Medium
0100-same-tree Easy
0101-symmetric-tree Easy
0102-binary-tree-level-order-traversal Medium
0103-binary-tree-zigzag-level-order-traversal Medium
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
0113-path-sum-ii Medium
0114-flatten-binary-tree-to-linked-list Medium
0116-populating-next-right-pointers-in-each-node Medium
0144-binary-tree-preorder-traversal Easy
0145-binary-tree-postorder-traversal Easy
0199-binary-tree-right-side-view Medium
0226-invert-binary-tree Easy
0230-kth-smallest-element-in-a-bst Medium
0235-lowest-common-ancestor-of-a-binary-search-tree Medium
0297-serialize-and-deserialize-binary-tree Hard
0450-delete-node-in-a-bst Medium
0543-diameter-of-binary-tree Easy
0637-average-of-levels-in-binary-tree Easy
0703-kth-largest-element-in-a-stream Easy
0987-vertical-order-traversal-of-a-binary-tree Hard

Depth-First Search

Problem Name Difficulty
0094-binary-tree-inorder-traversal Easy
0098-validate-binary-search-tree Medium
0100-same-tree Easy
0101-symmetric-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
0113-path-sum-ii Medium
0114-flatten-binary-tree-to-linked-list Medium
0116-populating-next-right-pointers-in-each-node Medium
0133-clone-graph Medium
0144-binary-tree-preorder-traversal Easy
0145-binary-tree-postorder-traversal Easy
0199-binary-tree-right-side-view Medium
0207-course-schedule Medium
0210-course-schedule-ii Medium
0211-design-add-and-search-words-data-structure Medium
0226-invert-binary-tree Easy
0230-kth-smallest-element-in-a-bst Medium
0235-lowest-common-ancestor-of-a-binary-search-tree Medium
0297-serialize-and-deserialize-binary-tree Hard
0310-minimum-height-trees Medium
0417-pacific-atlantic-water-flow Medium
0543-diameter-of-binary-tree Easy
0637-average-of-levels-in-binary-tree Easy
0684-redundant-connection Medium
0721-accounts-merge Medium
0797-all-paths-from-source-to-target Medium
0987-vertical-order-traversal-of-a-binary-tree Hard
1202-smallest-string-with-swaps Medium
1203-sort-items-by-groups-respecting-dependencies Hard

Binary Tree

Problem Name Difficulty
0094-binary-tree-inorder-traversal Easy
0098-validate-binary-search-tree Medium
0100-same-tree Easy
0101-symmetric-tree Easy
0102-binary-tree-level-order-traversal Medium
0103-binary-tree-zigzag-level-order-traversal Medium
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
0113-path-sum-ii Medium
0114-flatten-binary-tree-to-linked-list Medium
0116-populating-next-right-pointers-in-each-node Medium
0144-binary-tree-preorder-traversal Easy
0145-binary-tree-postorder-traversal Easy
0199-binary-tree-right-side-view Medium
0226-invert-binary-tree Easy
0230-kth-smallest-element-in-a-bst Medium
0235-lowest-common-ancestor-of-a-binary-search-tree Medium
0297-serialize-and-deserialize-binary-tree Hard
0450-delete-node-in-a-bst Medium
0543-diameter-of-binary-tree Easy
0637-average-of-levels-in-binary-tree Easy
0703-kth-largest-element-in-a-stream Easy
0987-vertical-order-traversal-of-a-binary-tree Hard

Hash Table

Problem Name Difficulty
0013-roman-to-integer Easy
0017-letter-combinations-of-a-phone-number Medium
0105-construct-binary-tree-from-preorder-and-inorder-traversal Medium
0106-construct-binary-tree-from-inorder-and-postorder-traversal Medium
0127-word-ladder Hard
0133-clone-graph Medium
0138-copy-list-with-random-pointer Medium
0139-word-break Medium
0169-majority-element Easy
0208-implement-trie-prefix-tree Medium
0217-contains-duplicate Easy
0219-contains-duplicate-ii Easy
0229-majority-element-ii Medium
0290-word-pattern Easy
0721-accounts-merge Medium
0752-open-the-lock Medium
0904-fruit-into-baskets Medium
0987-vertical-order-traversal-of-a-binary-tree Hard
1202-smallest-string-with-swaps Medium

Sorting

Problem Name Difficulty
0047-permutations-ii Medium
0169-majority-element Easy
0217-contains-duplicate Easy
0229-majority-element-ii Medium
0721-accounts-merge Medium
0987-vertical-order-traversal-of-a-binary-tree Hard
1202-smallest-string-with-swaps Medium

Binary Search Tree

Problem Name Difficulty
0098-validate-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
0703-kth-largest-element-in-a-stream Easy

Divide and Conquer

Problem Name Difficulty
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
0169-majority-element Easy

Graph Theory

Problem Name Difficulty
0133-clone-graph Medium
0207-course-schedule Medium
0210-course-schedule-ii Medium
0310-minimum-height-trees Medium
0684-redundant-connection Medium
0797-all-paths-from-source-to-target Medium
0990-satisfiability-of-equality-equations Medium
1203-sort-items-by-groups-respecting-dependencies Hard

Matrix

Problem Name Difficulty
0063-unique-paths-ii Medium
0304-range-sum-query-2d-immutable Medium
0417-pacific-atlantic-water-flow Medium
0909-snakes-and-ladders Medium
0994-rotting-oranges Medium
1091-shortest-path-in-binary-matrix Medium

Topological Sort

Problem Name Difficulty
0207-course-schedule Medium
0210-course-schedule-ii Medium
0310-minimum-height-trees Medium
1203-sort-items-by-groups-respecting-dependencies Hard

Union-Find

Problem Name Difficulty
0684-redundant-connection Medium
0721-accounts-merge Medium
0990-satisfiability-of-equality-equations Medium
1202-smallest-string-with-swaps Medium

Trie

Problem Name Difficulty
0139-word-break Medium
0208-implement-trie-prefix-tree Medium
0211-design-add-and-search-words-data-structure Medium

Bit Manipulation

Problem Name Difficulty
0029-divide-two-integers Medium
0067-add-binary Easy
0078-subsets Medium
0090-subsets-ii Medium
0526-beautiful-arrangement Medium
0698-partition-to-k-equal-sum-subsets Medium
0784-letter-case-permutation Medium

Two Pointers

Problem Name Difficulty
0005-longest-palindromic-substring Medium
0026-remove-duplicates-from-sorted-array Easy
0027-remove-element Easy
0031-next-permutation Medium

Bitmask

Problem Name Difficulty
0526-beautiful-arrangement Medium
0698-partition-to-k-equal-sum-subsets Medium

Brainteaser

Problem Name Difficulty
0292-nim-game Easy

Game Theory

Problem Name Difficulty
0292-nim-game Easy

Data Stream

Problem Name Difficulty
0703-kth-largest-element-in-a-stream Easy

Combinatorics

Problem Name Difficulty
0062-unique-paths Medium

Simulation

Problem Name Difficulty
0067-add-binary Easy
2073-time-needed-to-buy-tickets Easy

Database

Problem Name Difficulty
0197-rising-temperature Easy
0584-find-customer-referee Easy
0595-big-countries Easy
0620-not-boring-movies Easy
1068-product-sales-analysis-i Easy
1148-article-views-i Easy
1378-replace-employee-id-with-the-unique-identifier Easy
1581-customer-who-visited-but-did-not-make-any-transactions Easy
1683-invalid-tweets Easy
1757-recyclable-and-low-fat-products Easy

Counting

Problem Name Difficulty
0169-majority-element Easy
0229-majority-element-ii Medium

About

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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