leetcode

LeetCode Topics

Hash Table

Problem Name	Difficulty
0001-two-sum
0003-longest-substring-without-repeating-characters
0017-letter-combinations-of-a-phone-number
0036-valid-sudoku
0049-group-anagrams
0076-minimum-window-substring
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0127-word-ladder
0128-longest-consecutive-sequence
0133-clone-graph
0138-copy-list-with-random-pointer
0139-word-break
0141-linked-list-cycle
0146-lru-cache
0208-implement-trie-prefix-tree
0314-binary-tree-vertical-order-traversal
0347-top-k-frequent-elements
0355-design-twitter
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0567-permutation-in-string
0621-task-scheduler
0753-open-the-lock
0763-partition-labels
0846-hand-of-straights
0981-time-based-key-value-store
2516-take-k-of-each-character-from-left-and-right

String

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0014-longest-common-prefix
0017-letter-combinations-of-a-phone-number
0020-valid-parentheses
0022-generate-parentheses
0049-group-anagrams
0076-minimum-window-substring
0079-word-search
0091-decode-ways
0093-restore-ip-addresses
0125-valid-palindrome
0127-word-ladder
0131-palindrome-partitioning
0139-word-break
0151-reverse-words-in-a-string
0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure
0212-word-search-ii
0257-binary-tree-paths
0271-encode-and-decode-strings
0297-serialize-and-deserialize-binary-tree
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0567-permutation-in-string
0647-palindromic-substrings
0680-valid-palindrome-ii
0753-open-the-lock
0763-partition-labels
0981-time-based-key-value-store
1143-longest-common-subsequence
2516-take-k-of-each-character-from-left-and-right

Backtracking

Problem Name	Difficulty
0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0039-combination-sum
0040-combination-sum-ii
0046-permutations
0051-n-queens
0078-subsets
0079-word-search
0090-subsets-ii
0093-restore-ip-addresses
0113-path-sum-ii
0131-palindrome-partitioning
0212-word-search-ii
0257-binary-tree-paths

Dynamic Programming

Problem Name	Difficulty
0005-longest-palindromic-substring
0022-generate-parentheses
0042-trapping-rain-water
0045-jump-game-ii
0053-maximum-subarray
0055-jump-game
0062-unique-paths
0064-minimum-path-sum
0070-climbing-stairs
0091-decode-ways
0124-binary-tree-maximum-path-sum
0131-palindrome-partitioning
0139-word-break
0152-maximum-product-subarray
0198-house-robber
0213-house-robber-ii
0221-maximal-square
0300-longest-increasing-subsequence
0322-coin-change
0368-largest-divisible-subset
0416-partition-equal-subset-sum
0435-non-overlapping-intervals
0647-palindromic-substrings
0746-min-cost-climbing-stairs
0918-maximum-sum-circular-subarray
0978-longest-turbulent-subarray
1143-longest-common-subsequence

Array

Problem Name	Difficulty
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
0034-find-first-and-last-position-of-element-in-sorted-array
0036-valid-sudoku
0039-combination-sum
0040-combination-sum-ii
0042-trapping-rain-water
0045-jump-game-ii
0046-permutations
0049-group-anagrams
0051-n-queens
0053-maximum-subarray
0054-spiral-matrix
0055-jump-game
0056-merge-intervals
0057-insert-interval
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
0128-longest-consecutive-sequence
0130-surrounded-regions
0134-gas-station
0139-word-break
0152-maximum-product-subarray
0153-find-minimum-in-rotated-sorted-array
0167-two-sum-ii-input-array-is-sorted
0198-house-robber
0200-number-of-islands
0212-word-search-ii
0213-house-robber-ii
0215-kth-largest-element-in-an-array
0221-maximal-square
0238-product-of-array-except-self
0239-sliding-window-maximum
0252-meeting-rooms
0253-meeting-rooms-ii
0271-encode-and-decode-strings
0283-move-zeroes
0286-walls-and-gates
0287-find-the-duplicate-number
0300-longest-increasing-subsequence
0322-coin-change
0347-top-k-frequent-elements
0368-largest-divisible-subset
0416-partition-equal-subset-sum
0417-pacific-atlantic-water-flow
0419-battleships-in-a-board
0435-non-overlapping-intervals
0444-sequence-reconstruction
0540-single-element-in-a-sorted-array
0621-task-scheduler
0695-max-area-of-island
0704-binary-search	Easy
0729-my-calendar-i
0733-flood-fill
0739-daily-temperatures
0746-min-cost-climbing-stairs
0753-open-the-lock
0792-binary-search
0827-making-a-large-island
0846-hand-of-straights
0853-car-fleet
0875-koko-eating-bananas
0907-koko-eating-bananas
0918-maximum-sum-circular-subarray
0973-k-closest-points-to-origin
0978-longest-turbulent-subarray
0994-rotting-oranges
1036-rotting-oranges
1046-last-stone-weight
1091-shortest-path-in-binary-matrix
1475-final-prices-with-a-special-discount-in-a-shop
1514-path-with-maximum-probability
1584-min-cost-to-connect-all-points
1899-merge-triplets-to-form-target-triplet
2530-maximal-score-after-applying-k-operations

Trie

Problem Name	Difficulty
0014-longest-common-prefix
0139-word-break
0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure
0212-word-search-ii

Memoization

Problem Name	Difficulty
0070-climbing-stairs
0139-word-break

Breadth-First Search

Problem Name	Difficulty
0100-same-tree
0102-binary-tree-level-order-traversal
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0116-populating-next-right-pointers-in-each-node
0127-word-ladder
0130-surrounded-regions
0133-clone-graph
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0210-course-schedule-ii
0226-invert-binary-tree
0261-graph-valid-tree
0286-walls-and-gates
0297-serialize-and-deserialize-binary-tree
0314-binary-tree-vertical-order-traversal
0322-coin-change
0323-number-of-connected-components-in-an-undirected-graph
0417-pacific-atlantic-water-flow
0684-redundant-connection
0695-max-area-of-island
0733-flood-fill
0743-network-delay-time
0753-open-the-lock
0827-making-a-large-island
0841-keys-and-rooms
0994-rotting-oranges
1036-rotting-oranges
1091-shortest-path-in-binary-matrix
1142-minimum-knight-moves
1448-count-good-nodes-in-binary-tree
1544-count-good-nodes-in-binary-tree
2415-reverse-odd-levels-of-binary-tree

Tree

Problem Name	Difficulty
0098-validate-binary-search-tree
0100-same-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
0110-balanced-binary-tree
0113-path-sum-ii
0116-populating-next-right-pointers-in-each-node
0124-binary-tree-maximum-path-sum
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
0297-serialize-and-deserialize-binary-tree
0314-binary-tree-vertical-order-traversal
0450-delete-node-in-a-bst
0543-diameter-of-binary-tree
0572-subtree-of-another-tree
0703-kth-largest-element-in-a-stream
0784-insert-into-a-binary-search-tree
1038-binary-search-tree-to-greater-sum-tree
1448-count-good-nodes-in-binary-tree
1544-count-good-nodes-in-binary-tree
2415-reverse-odd-levels-of-binary-tree

Depth-First Search

Problem Name	Difficulty
0079-word-search
0098-validate-binary-search-tree
0100-same-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0113-path-sum-ii
0116-populating-next-right-pointers-in-each-node
0124-binary-tree-maximum-path-sum
0130-surrounded-regions
0133-clone-graph
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0210-course-schedule-ii
0211-design-add-and-search-words-data-structure
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
0261-graph-valid-tree
0297-serialize-and-deserialize-binary-tree
0314-binary-tree-vertical-order-traversal
0323-number-of-connected-components-in-an-undirected-graph
0417-pacific-atlantic-water-flow
0419-battleships-in-a-board
0543-diameter-of-binary-tree
0572-subtree-of-another-tree
0684-redundant-connection
0695-max-area-of-island
0733-flood-fill
0743-network-delay-time
0827-making-a-large-island
0841-keys-and-rooms
1038-binary-search-tree-to-greater-sum-tree
1448-count-good-nodes-in-binary-tree
1544-count-good-nodes-in-binary-tree
2415-reverse-odd-levels-of-binary-tree

Binary Tree

Problem Name	Difficulty
0098-validate-binary-search-tree
0100-same-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
0110-balanced-binary-tree
0113-path-sum-ii
0116-populating-next-right-pointers-in-each-node
0124-binary-tree-maximum-path-sum
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
0297-serialize-and-deserialize-binary-tree
0314-binary-tree-vertical-order-traversal
0450-delete-node-in-a-bst
0543-diameter-of-binary-tree
0572-subtree-of-another-tree
0703-kth-largest-element-in-a-stream
0784-insert-into-a-binary-search-tree
1038-binary-search-tree-to-greater-sum-tree
1448-count-good-nodes-in-binary-tree
1544-count-good-nodes-in-binary-tree
2415-reverse-odd-levels-of-binary-tree

Matrix

Problem Name	Difficulty
0036-valid-sudoku
0054-spiral-matrix
0064-minimum-path-sum
0074-search-a-2d-matrix
0079-word-search
0130-surrounded-regions
0200-number-of-islands
0212-word-search-ii
0221-maximal-square
0286-walls-and-gates
0417-pacific-atlantic-water-flow
0419-battleships-in-a-board
0695-max-area-of-island
0733-flood-fill
0827-making-a-large-island
0994-rotting-oranges
1036-rotting-oranges
1091-shortest-path-in-binary-matrix

Union Find

Problem Name	Difficulty
0130-surrounded-regions
0200-number-of-islands
0261-graph-valid-tree

Graph

Problem Name	Difficulty
0207-course-schedule
0210-course-schedule-ii
0261-graph-valid-tree
0444-sequence-reconstruction

Topological Sort

Problem Name	Difficulty
0207-course-schedule
0210-course-schedule-ii
0444-sequence-reconstruction

Math

Problem Name	Difficulty
0002-add-two-numbers
0009-palindrome-number
0062-unique-paths
0070-climbing-stairs
0368-largest-divisible-subset
0973-k-closest-points-to-origin

Combinatorics

Problem Name	Difficulty
0062-unique-paths

Sorting

Problem Name	Difficulty
0015-3sum
0049-group-anagrams
0056-merge-intervals
0215-kth-largest-element-in-an-array
0252-meeting-rooms
0253-meeting-rooms-ii
0314-binary-tree-vertical-order-traversal
0347-top-k-frequent-elements
0368-largest-divisible-subset
0435-non-overlapping-intervals
0621-task-scheduler
0846-hand-of-straights
0853-car-fleet
0973-k-closest-points-to-origin

Binary Search

Problem Name	Difficulty
0004-median-of-two-sorted-arrays
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0074-search-a-2d-matrix
0153-find-minimum-in-rotated-sorted-array
0167-two-sum-ii-input-array-is-sorted
0287-find-the-duplicate-number
0300-longest-increasing-subsequence
0540-single-element-in-a-sorted-array
0704-binary-search	Easy
0729-my-calendar-i
0792-binary-search
0875-koko-eating-bananas
0907-koko-eating-bananas
0981-time-based-key-value-store

Design

Problem Name	Difficulty
0146-lru-cache
0155-min-stack
0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure
0271-encode-and-decode-strings
0297-serialize-and-deserialize-binary-tree
0355-design-twitter
0703-kth-largest-element-in-a-stream
0729-my-calendar-i
0981-time-based-key-value-store

Segment Tree

Problem Name	Difficulty
0729-my-calendar-i

Ordered Set

Problem Name	Difficulty
0729-my-calendar-i

Two Pointers

Problem Name	Difficulty
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
0143-reorder-list
0151-reverse-words-in-a-string
0167-two-sum-ii-input-array-is-sorted
0253-meeting-rooms-ii
0283-move-zeroes
0287-find-the-duplicate-number
0567-permutation-in-string
0647-palindromic-substrings
0680-valid-palindrome-ii
0763-partition-labels
2095-delete-the-middle-node-of-a-linked-list

Greedy

Problem Name	Difficulty
0011-container-with-most-water
0045-jump-game-ii
0055-jump-game
0134-gas-station
0253-meeting-rooms-ii
0435-non-overlapping-intervals
0621-task-scheduler
0680-valid-palindrome-ii
0763-partition-labels
0846-hand-of-straights
1899-merge-triplets-to-form-target-triplet
2530-maximal-score-after-applying-k-operations

Sliding Window

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters
0076-minimum-window-substring
0239-sliding-window-maximum
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0567-permutation-in-string
0978-longest-turbulent-subarray
2516-take-k-of-each-character-from-left-and-right

Prefix Sum

Problem Name	Difficulty
0238-product-of-array-except-self
0253-meeting-rooms-ii

String Matching

Problem Name	Difficulty
0572-subtree-of-another-tree

Hash Function

Problem Name	Difficulty
0572-subtree-of-another-tree

Binary Search Tree

Problem Name	Difficulty
0098-validate-binary-search-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0450-delete-node-in-a-bst
0703-kth-largest-element-in-a-stream
0784-insert-into-a-binary-search-tree
1038-binary-search-tree-to-greater-sum-tree

Bit Manipulation

Problem Name	Difficulty
0078-subsets
0090-subsets-ii
0287-find-the-duplicate-number

Linked List

Problem Name	Difficulty
0002-add-two-numbers
0019-remove-nth-node-from-end-of-list
0021-merge-two-sorted-lists
0023-merge-k-sorted-lists
0025-reverse-nodes-in-k-group
0116-populating-next-right-pointers-in-each-node
0138-copy-list-with-random-pointer
0141-linked-list-cycle
0143-reorder-list
0146-lru-cache
0355-design-twitter
2095-delete-the-middle-node-of-a-linked-list

Doubly-Linked List

Problem Name	Difficulty
0146-lru-cache

Recursion

Problem Name	Difficulty
0002-add-two-numbers
0021-merge-two-sorted-lists
0025-reverse-nodes-in-k-group
0143-reorder-list

Divide and Conquer

Problem Name	Difficulty
0004-median-of-two-sorted-arrays
0023-merge-k-sorted-lists
0053-maximum-subarray
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
0918-maximum-sum-circular-subarray
0973-k-closest-points-to-origin

Heap (Priority Queue)

Problem Name	Difficulty
0023-merge-k-sorted-lists
0215-kth-largest-element-in-an-array
0239-sliding-window-maximum
0253-meeting-rooms-ii
0347-top-k-frequent-elements
0355-design-twitter
0621-task-scheduler
0703-kth-largest-element-in-a-stream
0743-network-delay-time
0973-k-closest-points-to-origin
1046-last-stone-weight
1514-path-with-maximum-probability
2530-maximal-score-after-applying-k-operations

Data Stream

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

Geometry

Problem Name	Difficulty
0973-k-closest-points-to-origin

Quickselect

Problem Name	Difficulty
0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
0973-k-closest-points-to-origin

Counting

Problem Name	Difficulty
0347-top-k-frequent-elements
0621-task-scheduler

Graph Theory

Problem Name	Difficulty
0133-clone-graph
0207-course-schedule
0210-course-schedule-ii
0261-graph-valid-tree
0323-number-of-connected-components-in-an-undirected-graph
0684-redundant-connection
0743-network-delay-time
0841-keys-and-rooms
1514-path-with-maximum-probability
1584-min-cost-to-connect-all-points

Union-Find

Problem Name	Difficulty
0128-longest-consecutive-sequence
0130-surrounded-regions
0200-number-of-islands
0261-graph-valid-tree
0323-number-of-connected-components-in-an-undirected-graph
0684-redundant-connection
0695-max-area-of-island
0827-making-a-large-island
1584-min-cost-to-connect-all-points

Queue

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

Monotonic Queue

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

Stack

Problem Name	Difficulty
0020-valid-parentheses
0042-trapping-rain-water
0143-reorder-list
0155-min-stack
0739-daily-temperatures
0853-car-fleet
1475-final-prices-with-a-special-discount-in-a-shop

Monotonic Stack

Problem Name	Difficulty
0042-trapping-rain-water
0739-daily-temperatures
0853-car-fleet
1475-final-prices-with-a-special-discount-in-a-shop

Bucket Sort

Problem Name	Difficulty
0347-top-k-frequent-elements

Shortest Path

Problem Name	Difficulty
0743-network-delay-time
1514-path-with-maximum-probability

Minimum Spanning Tree

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

Merge Sort

Problem Name	Difficulty
0023-merge-k-sorted-lists

Simulation

Problem Name	Difficulty
0054-spiral-matrix