A collection of LeetCode questions

LeetCode Topics

Array

0001-two-sum
0004-median-of-two-sorted-arrays
0011-container-with-most-water
0014-longest-common-prefix
0015-3sum
0033-search-in-rotated-sorted-array
0035-search-insert-position
0036-valid-sudoku
0039-combination-sum
0040-combination-sum-ii
0042-trapping-rain-water
0045-jump-game-ii
0046-permutations
0047-permutations-ii
0049-group-anagrams
0051-n-queens
0053-maximum-subarray
0054-spiral-matrix
0055-jump-game
0056-merge-intervals
0057-insert-interval
0063-unique-paths-ii
0064-minimum-path-sum
0074-search-a-2d-matrix
0078-subsets
0079-word-search
0090-subsets-ii
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0121-best-time-to-buy-and-sell-stock
0122-best-time-to-buy-and-sell-stock-ii
0128-longest-consecutive-sequence
0130-surrounded-regions
0139-word-break
0150-evaluate-reverse-polish-notation
0152-maximum-product-subarray
0153-find-minimum-in-rotated-sorted-array
0167-two-sum-ii-input-array-is-sorted
0169-majority-element
0174-dungeon-game
0198-house-robber
0200-number-of-islands
0209-minimum-size-subarray-sum
0213-house-robber-ii
0215-kth-largest-element-in-an-array
0217-contains-duplicate
0228-summary-ranges
0238-product-of-array-except-self
0300-longest-increasing-subsequence
0309-best-time-to-buy-and-sell-stock-with-cooldown
0322-coin-change
0329-longest-increasing-path-in-a-matrix
0334-increasing-triplet-subsequence
0347-top-k-frequent-elements
0416-partition-equal-subset-sum
0417-pacific-atlantic-water-flow
0435-non-overlapping-intervals
0485-max-consecutive-ones
0494-target-sum
0496-next-greater-element-i
0518-coin-change-ii
0621-task-scheduler
0643-maximum-average-subarray-i
0682-baseball-game
0695-max-area-of-island
0739-daily-temperatures
0747-min-cost-climbing-stairs
0753-open-the-lock
0792-binary-search
0794-swim-in-rising-water
0907-koko-eating-bananas
1014-k-closest-points-to-origin
1019-squares-of-a-sorted-array
1036-rotting-oranges
1046-max-consecutive-ones-iii
1127-last-stone-weight
1171-shortest-path-in-binary-matrix
1428-jump-game-iii
1706-min-cost-to-connect-all-points
1753-path-with-minimum-effort
1977-minimum-interval-to-include-each-query
2113-find-the-kth-largest-integer-in-the-array
2250-k-highest-ranked-items-within-a-price-range
2350-find-closest-number-to-zero

Two Pointers

0005-longest-palindromic-substring
0011-container-with-most-water
0015-3sum
0019-remove-nth-node-from-end-of-list
0042-trapping-rain-water
0125-valid-palindrome
0141-linked-list-cycle
0142-linked-list-cycle-ii
0167-two-sum-ii-input-array-is-sorted
0295-find-median-from-data-stream
0344-reverse-string
0392-is-subsequence
0567-permutation-in-string
0647-palindromic-substrings
0908-middle-of-the-linked-list
1019-squares-of-a-sorted-array
1894-merge-strings-alternately
2216-delete-the-middle-node-of-a-linked-list

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0013-roman-to-integer
0014-longest-common-prefix
0017-letter-combinations-of-a-phone-number
0020-valid-parentheses
0022-generate-parentheses
0049-group-anagrams
0079-word-search
0097-interleaving-string
0115-distinct-subsequences
0125-valid-palindrome
0127-word-ladder
0131-palindrome-partitioning
0139-word-break
0242-valid-anagram
0257-binary-tree-paths
0344-reverse-string
0383-ransom-note
0392-is-subsequence
0424-longest-repeating-character-replacement
0433-minimum-genetic-mutation
0567-permutation-in-string
0647-palindromic-substrings
0753-open-the-lock
0778-reorganize-string
0782-jewels-and-stones
1250-longest-common-subsequence
1297-maximum-number-of-balloons
1894-merge-strings-alternately
2113-find-the-kth-largest-integer-in-the-array

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0013-roman-to-integer
0017-letter-combinations-of-a-phone-number
0036-valid-sudoku
0049-group-anagrams
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0127-word-ladder
0128-longest-consecutive-sequence
0139-word-break
0141-linked-list-cycle
0142-linked-list-cycle-ii
0146-lru-cache
0169-majority-element
0217-contains-duplicate
0242-valid-anagram
0347-top-k-frequent-elements
0383-ransom-note
0424-longest-repeating-character-replacement
0433-minimum-genetic-mutation
0496-next-greater-element-i
0508-most-frequent-subtree-sum
0567-permutation-in-string
0621-task-scheduler
0753-open-the-lock
0778-reorganize-string
0782-jewels-and-stones
1297-maximum-number-of-balloons

Math

0013-roman-to-integer
0062-unique-paths
0070-climbing-stairs
0150-evaluate-reverse-polish-notation
0367-valid-perfect-square
1013-fibonacci-number
1014-k-closest-points-to-origin
2903-insert-greatest-common-divisors-in-linked-list

Dynamic Programming

0005-longest-palindromic-substring
0022-generate-parentheses
0042-trapping-rain-water
0045-jump-game-ii
0053-maximum-subarray
0055-jump-game
0062-unique-paths
0063-unique-paths-ii
0064-minimum-path-sum
0070-climbing-stairs
0097-interleaving-string
0115-distinct-subsequences
0121-best-time-to-buy-and-sell-stock
0122-best-time-to-buy-and-sell-stock-ii
0124-binary-tree-maximum-path-sum
0131-palindrome-partitioning
0139-word-break
0152-maximum-product-subarray
0174-dungeon-game
0198-house-robber
0213-house-robber-ii
0300-longest-increasing-subsequence
0309-best-time-to-buy-and-sell-stock-with-cooldown
0322-coin-change
0329-longest-increasing-path-in-a-matrix
0392-is-subsequence
0416-partition-equal-subset-sum
0435-non-overlapping-intervals
0494-target-sum
0518-coin-change-ii
0647-palindromic-substrings
0747-min-cost-climbing-stairs
0803-cheapest-flights-within-k-stops
1013-fibonacci-number
1250-longest-common-subsequence

Trie

0014-longest-common-prefix
0139-word-break

Prefix Sum

0209-minimum-size-subarray-sum
0238-product-of-array-except-self
1046-max-consecutive-ones-iii

Sorting

0015-3sum
0047-permutations-ii
0049-group-anagrams
0056-merge-intervals
0169-majority-element
0215-kth-largest-element-in-an-array
0217-contains-duplicate
0242-valid-anagram
0295-find-median-from-data-stream
0347-top-k-frequent-elements
0435-non-overlapping-intervals
0621-task-scheduler
0778-reorganize-string
1014-k-closest-points-to-origin
1019-squares-of-a-sorted-array
1977-minimum-interval-to-include-each-query
2113-find-the-kth-largest-integer-in-the-array
2250-k-highest-ranked-items-within-a-price-range

Matrix

0036-valid-sudoku
0054-spiral-matrix
0063-unique-paths-ii
0064-minimum-path-sum
0074-search-a-2d-matrix
0079-word-search
0130-surrounded-regions
0174-dungeon-game
0200-number-of-islands
0329-longest-increasing-path-in-a-matrix
0417-pacific-atlantic-water-flow
0695-max-area-of-island
0794-swim-in-rising-water
1036-rotting-oranges
1171-shortest-path-in-binary-matrix
1753-path-with-minimum-effort
2250-k-highest-ranked-items-within-a-price-range

Simulation

0054-spiral-matrix
0682-baseball-game

Counting

0169-majority-element
0347-top-k-frequent-elements
0383-ransom-note
0621-task-scheduler
0778-reorganize-string
1297-maximum-number-of-balloons

Divide and Conquer

0004-median-of-two-sorted-arrays
0023-merge-k-sorted-lists
0053-maximum-subarray
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0169-majority-element
0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
1014-k-closest-points-to-origin
2113-find-the-kth-largest-integer-in-the-array

Binary Search

0004-median-of-two-sorted-arrays
0033-search-in-rotated-sorted-array
0035-search-insert-position
0074-search-a-2d-matrix
0153-find-minimum-in-rotated-sorted-array
0167-two-sum-ii-input-array-is-sorted
0209-minimum-size-subarray-sum
0278-first-bad-version
0300-longest-increasing-subsequence
0367-valid-perfect-square
0792-binary-search
0794-swim-in-rising-water
0907-koko-eating-bananas
1046-max-consecutive-ones-iii
1753-path-with-minimum-effort
1977-minimum-interval-to-include-each-query

Greedy

0011-container-with-most-water
0045-jump-game-ii
0055-jump-game
0122-best-time-to-buy-and-sell-stock-ii
0334-increasing-triplet-subsequence
0435-non-overlapping-intervals
0621-task-scheduler
0778-reorganize-string

Stack

0020-valid-parentheses
0042-trapping-rain-water
0094-binary-tree-inorder-traversal
0150-evaluate-reverse-polish-notation
0155-min-stack
0496-next-greater-element-i
0682-baseball-game
0739-daily-temperatures

Monotonic Stack

0042-trapping-rain-water
0496-next-greater-element-i
0739-daily-temperatures

Design

0146-lru-cache
0155-min-stack
0295-find-median-from-data-stream
0789-kth-largest-element-in-a-stream

Interactive

0278-first-bad-version

Linked List

0019-remove-nth-node-from-end-of-list
0021-merge-two-sorted-lists
0023-merge-k-sorted-lists
0083-remove-duplicates-from-sorted-list
0109-convert-sorted-list-to-binary-search-tree
0116-populating-next-right-pointers-in-each-node
0141-linked-list-cycle
0142-linked-list-cycle-ii
0146-lru-cache
0206-reverse-linked-list
0908-middle-of-the-linked-list
2216-delete-the-middle-node-of-a-linked-list
2903-insert-greatest-common-divisors-in-linked-list

Recursion

0021-merge-two-sorted-lists
0206-reverse-linked-list
1013-fibonacci-number

Number Theory

2903-insert-greatest-common-divisors-in-linked-list

Sliding Window

0003-longest-substring-without-repeating-characters
0209-minimum-size-subarray-sum
0424-longest-repeating-character-replacement
0567-permutation-in-string
0643-maximum-average-subarray-i
1046-max-consecutive-ones-iii

Union Find

0128-longest-consecutive-sequence
0130-surrounded-regions
0200-number-of-islands
0547-number-of-provinces
0684-redundant-connection
0695-max-area-of-island
0794-swim-in-rising-water
1706-min-cost-to-connect-all-points
1753-path-with-minimum-effort
2121-find-if-path-exists-in-graph

Tree

0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0100-same-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
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0107-binary-tree-level-order-traversal-ii
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0116-populating-next-right-pointers-in-each-node
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0199-binary-tree-right-side-view
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0257-binary-tree-paths
0508-most-frequent-subtree-sum
0530-minimum-absolute-difference-in-bst
0543-diameter-of-binary-tree
0572-subtree-of-another-tree
0764-n-ary-tree-level-order-traversal
0789-kth-largest-element-in-a-stream
1544-count-good-nodes-in-binary-tree

Depth-First Search

0079-word-search
0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0100-same-tree
0101-symmetric-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0116-populating-next-right-pointers-in-each-node
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0130-surrounded-regions
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0210-course-schedule-ii
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0257-binary-tree-paths
0329-longest-increasing-path-in-a-matrix
0332-reconstruct-itinerary
0417-pacific-atlantic-water-flow
0508-most-frequent-subtree-sum
0530-minimum-absolute-difference-in-bst
0543-diameter-of-binary-tree
0547-number-of-provinces
0572-subtree-of-another-tree
0684-redundant-connection
0695-max-area-of-island
0744-network-delay-time
0794-swim-in-rising-water
0803-cheapest-flights-within-k-stops
0820-find-eventual-safe-states
1428-jump-game-iii
1544-count-good-nodes-in-binary-tree
1558-course-schedule-iv
1753-path-with-minimum-effort
2121-find-if-path-exists-in-graph

Breadth-First Search

0100-same-tree
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
0127-word-ladder
0130-surrounded-regions
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0210-course-schedule-ii
0226-invert-binary-tree
0322-coin-change
0329-longest-increasing-path-in-a-matrix
0417-pacific-atlantic-water-flow
0433-minimum-genetic-mutation
0530-minimum-absolute-difference-in-bst
0547-number-of-provinces
0684-redundant-connection
0695-max-area-of-island
0744-network-delay-time
0753-open-the-lock
0764-n-ary-tree-level-order-traversal
0794-swim-in-rising-water
0803-cheapest-flights-within-k-stops
0820-find-eventual-safe-states
1036-rotting-oranges
1171-shortest-path-in-binary-matrix
1428-jump-game-iii
1544-count-good-nodes-in-binary-tree
1558-course-schedule-iv
1753-path-with-minimum-effort
2121-find-if-path-exists-in-graph
2250-k-highest-ranked-items-within-a-price-range

Binary Tree

0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0100-same-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
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0107-binary-tree-level-order-traversal-ii
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree
0111-minimum-depth-of-binary-tree
0112-path-sum
0113-path-sum-ii
0116-populating-next-right-pointers-in-each-node
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0199-binary-tree-right-side-view
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0257-binary-tree-paths
0508-most-frequent-subtree-sum
0530-minimum-absolute-difference-in-bst
0543-diameter-of-binary-tree
0572-subtree-of-another-tree
0789-kth-largest-element-in-a-stream
1544-count-good-nodes-in-binary-tree

String Matching

0572-subtree-of-another-tree

Hash Function

0572-subtree-of-another-tree

Binary Search Tree

0098-validate-binary-search-tree
0108-convert-sorted-array-to-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0530-minimum-absolute-difference-in-bst
0789-kth-largest-element-in-a-stream

Heap (Priority Queue)

0023-merge-k-sorted-lists
0215-kth-largest-element-in-an-array
0295-find-median-from-data-stream
0347-top-k-frequent-elements
0621-task-scheduler
0744-network-delay-time
0778-reorganize-string
0789-kth-largest-element-in-a-stream
0794-swim-in-rising-water
0803-cheapest-flights-within-k-stops
1014-k-closest-points-to-origin
1127-last-stone-weight
1753-path-with-minimum-effort
1977-minimum-interval-to-include-each-query
2113-find-the-kth-largest-integer-in-the-array
2250-k-highest-ranked-items-within-a-price-range

Quickselect

0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
1014-k-closest-points-to-origin
2113-find-the-kth-largest-integer-in-the-array

Bucket Sort

0347-top-k-frequent-elements

Geometry

1014-k-closest-points-to-origin

Merge Sort

0023-merge-k-sorted-lists

Backtracking

0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0039-combination-sum
0040-combination-sum-ii
0046-permutations
0047-permutations-ii
0051-n-queens
0077-combinations
0078-subsets
0079-word-search
0090-subsets-ii
0113-path-sum-ii
0131-palindrome-partitioning
0257-binary-tree-paths
0494-target-sum

Bit Manipulation

0078-subsets
0090-subsets-ii

Graph

0207-course-schedule
0210-course-schedule-ii
0329-longest-increasing-path-in-a-matrix
0332-reconstruct-itinerary
0547-number-of-provinces
0684-redundant-connection
0744-network-delay-time
0803-cheapest-flights-within-k-stops
0820-find-eventual-safe-states
1558-course-schedule-iv
1706-min-cost-to-connect-all-points
2121-find-if-path-exists-in-graph

Topological Sort

0207-course-schedule
0210-course-schedule-ii
0329-longest-increasing-path-in-a-matrix
0820-find-eventual-safe-states
1558-course-schedule-iv

Minimum Spanning Tree

1706-min-cost-to-connect-all-points

Shortest Path

0744-network-delay-time
0803-cheapest-flights-within-k-stops

Memoization

0070-climbing-stairs
0139-word-break
0329-longest-increasing-path-in-a-matrix
1013-fibonacci-number

Combinatorics

0062-unique-paths

Doubly-Linked List

0146-lru-cache

Eulerian Circuit

0332-reconstruct-itinerary

Line Sweep

1977-minimum-interval-to-include-each-query

Data Stream

0295-find-median-from-data-stream
0789-kth-largest-element-in-a-stream