LeetCode Topics

Array

0001-two-sum
0011-container-with-most-water
0031-next-permutation
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0036-valid-sudoku
0041-first-missing-positive
0049-group-anagrams
0053-maximum-subarray
0054-spiral-matrix
0059-spiral-matrix-ii
0073-set-matrix-zeroes
0075-sort-colors
0081-search-in-rotated-sorted-array-ii
0118-pascals-triangle
0121-best-time-to-buy-and-sell-stock
0128-longest-consecutive-sequence
0135-candy
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0169-majority-element
0189-rotate-array
0200-number-of-islands
0217-contains-duplicate
0229-majority-element-ii
0238-product-of-array-except-self
0347-top-k-frequent-elements
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0540-single-element-in-a-sorted-array
0594-longest-harmonious-subsequence
0745-find-smallest-letter-greater-than-target
0792-binary-search
0797-rabbits-in-forest
0882-peak-index-in-a-mountain-array
0921-spiral-matrix-iii
0924-fair-candy-swap
0934-bitwise-ors-of-subarrays
0940-fruit-into-baskets
0945-snakes-and-ladders
1049-minimum-domino-rotations-for-equal-row
1227-number-of-equivalent-domino-pairs
1293-three-consecutive-odds
1350-remove-sub-folders-from-the-filesystem
1372-check-if-it-is-a-good-array
1421-find-numbers-with-even-number-of-digits
1424-maximum-candies-you-can-get-from-boxes
1468-check-if-n-and-its-double-exist
1476-count-negative-numbers-in-a-sorted-matrix
1478-maximum-number-of-events-that-can-be-attended
1482-how-many-numbers-are-smaller-than-the-current-number
1505-create-target-array-in-the-given-order
1510-find-lucky-integer-in-an-array
1528-kids-with-the-greatest-number-of-candies
1580-shuffle-the-array
1603-running-sum-of-1d-array
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1635-number-of-good-pairs
1646-kth-missing-positive-number
1656-count-good-triplets
1730-special-array-with-x-elements-greater-than-or-equal-x
1791-richest-customer-wealth
1813-maximum-erasure-value
1851-maximum-number-of-events-that-can-be-attended-ii
1995-finding-pairs-with-a-certain-sum
2048-build-array-from-permutation
2058-concatenation-of-array
2079-delete-duplicate-folders-in-system
2144-maximum-difference-between-increasing-elements
2150-kth-smallest-product-of-two-sorted-arrays
2170-count-number-of-maximum-bitwise-or-subsets
2180-maximum-number-of-tasks-you-can-assign
2204-find-subsequence-of-length-k-with-the-largest-sum
2215-finding-3-digit-even-numbers
2229-maximum-fruits-harvested-after-at-most-k-steps
2237-longest-palindrome-by-concatenating-two-letter-words
2249-count-the-hidden-sequences
2267-minimum-difference-in-sums-after-removal-of-elements
2277-count-equal-and-divisible-pairs-in-an-array
2316-count-hills-and-valleys-in-an-array
2320-find-all-k-distant-indices-in-an-array
2387-partition-array-such-that-maximum-difference-is-k
2400-minimum-score-after-removals-on-a-tree
2479-meeting-rooms-iii
2498-smallest-subarrays-with-maximum-bitwise-or
2503-longest-subarray-with-maximum-bitwise-and
2527-count-subarrays-with-fixed-bounds
2626-count-the-number-of-good-subarrays
2689-rearranging-fruits
2699-count-the-number-of-fair-pairs
2720-minimize-the-maximum-difference-of-pairs
2856-count-complete-subarrays-in-an-array
3142-longest-unequal-adjacent-groups-subsequence-ii
3143-longest-unequal-adjacent-groups-subsequence-i
3171-minimum-equal-sum-of-two-arrays-after-replacing-zeros
3194-find-words-containing-character
3213-count-subarrays-where-max-element-appears-at-least-k-times
3241-divide-array-into-arrays-with-max-difference
3307-find-the-maximum-sum-of-node-values
3321-type-of-triangle
3490-find-the-maximum-length-of-valid-subsequence-i
3491-find-the-maximum-length-of-valid-subsequence-ii
3627-find-minimum-time-to-reach-last-room-i
3628-find-minimum-time-to-reach-last-room-ii
3639-zero-array-transformation-i
3647-zero-array-transformation-iii
3741-reschedule-meetings-for-maximum-free-time-ii
3743-reschedule-meetings-for-maximum-free-time-i
3747-maximum-difference-between-adjacent-elements-in-a-circular-array
3788-maximum-unique-subarray-sum-after-deletion
3789-maximize-subarrays-after-removing-one-conflicting-pair

Simulation

0054-spiral-matrix
0059-spiral-matrix-ii
0921-spiral-matrix-iii
1505-create-target-array-in-the-given-order
2048-build-array-from-permutation
2058-concatenation-of-array
2260-divide-a-string-into-groups-of-size-k
2479-meeting-rooms-iii
3600-find-the-k-th-character-in-string-game-i

Prefix Sum

0238-product-of-array-except-self
1603-running-sum-of-1d-array
2229-maximum-fruits-harvested-after-at-most-k-steps
2249-count-the-hidden-sequences
3618-find-the-original-typed-string-ii
3639-zero-array-transformation-i
3647-zero-array-transformation-iii
3761-maximum-difference-between-even-and-odd-frequency-ii
3789-maximize-subarrays-after-removing-one-conflicting-pair

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0036-valid-sudoku
0041-first-missing-positive
0049-group-anagrams
0073-set-matrix-zeroes
0128-longest-consecutive-sequence
0141-linked-list-cycle
0160-intersection-of-two-linked-lists
0169-majority-element
0217-contains-duplicate
0229-majority-element-ii
0242-valid-anagram
0347-top-k-frequent-elements
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0594-longest-harmonious-subsequence
0797-rabbits-in-forest
0924-fair-candy-swap
0940-fruit-into-baskets
1218-lowest-common-ancestor-of-deepest-leaves
1227-number-of-equivalent-domino-pairs
1468-check-if-n-and-its-double-exist
1482-how-many-numbers-are-smaller-than-the-current-number
1500-count-largest-group
1510-find-lucky-integer-in-an-array
1635-number-of-good-pairs
1813-maximum-erasure-value
1986-largest-color-value-in-a-directed-graph
1995-finding-pairs-with-a-certain-sum
2079-delete-duplicate-folders-in-system
2204-find-subsequence-of-length-k-with-the-largest-sum
2215-finding-3-digit-even-numbers
2237-longest-palindrome-by-concatenating-two-letter-words
2479-meeting-rooms-iii
2520-using-a-robot-to-print-the-lexicographically-smallest-string
2626-count-the-number-of-good-subarrays
2689-rearranging-fruits
2856-count-complete-subarrays-in-an-array
3360-minimum-deletions-to-make-string-k-special
3445-lexicographically-minimum-string-after-removing-stars
3629-total-characters-in-string-after-transformations-i
3630-total-characters-in-string-after-transformations-ii
3753-maximum-difference-between-even-and-odd-frequency-i
3754-maximum-manhattan-distance-after-k-changes
3788-maximum-unique-subarray-sum-after-deletion

Math

0069-sqrtx
0189-rotate-array
0367-valid-perfect-square
0441-arranging-coins
0797-rabbits-in-forest
1372-check-if-it-is-a-good-array
1411-convert-binary-number-in-a-linked-list-to-integer
1421-find-numbers-with-even-number-of-digits
1500-count-largest-group
1529-max-difference-you-can-get-from-changing-an-integer
1635-number-of-good-pairs
2202-sum-of-k-mirror-numbers
2415-count-the-number-of-ideal-arrays
2704-maximum-difference-by-remapping-a-digit
3172-divisible-and-non-divisible-sums-difference
3201-distribute-candies-among-children-ii
3321-type-of-triangle
3600-find-the-k-th-character-in-string-game-i
3601-find-the-k-th-character-in-string-game-ii
3629-total-characters-in-string-after-transformations-i
3630-total-characters-in-string-after-transformations-ii
3637-count-number-of-balanced-permutations
3682-count-the-number-of-arrays-with-k-matching-adjacent-elements
3754-maximum-manhattan-distance-after-k-changes

Two Pointers

0005-longest-palindromic-substring
0011-container-with-most-water
0019-remove-nth-node-from-end-of-list
0031-next-permutation
0075-sort-colors
0125-valid-palindrome
0141-linked-list-cycle
0160-intersection-of-two-linked-lists
0167-two-sum-ii-input-array-is-sorted
0189-rotate-array
0344-reverse-string
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0868-push-dominoes
1468-check-if-n-and-its-double-exist
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
2320-find-all-k-distant-indices-in-an-array
2699-count-the-number-of-fair-pairs
3683-find-the-lexicographically-largest-string-from-the-box-i

Sorting

0049-group-anagrams
0075-sort-colors
0169-majority-element
0217-contains-duplicate
0229-majority-element-ii
0242-valid-anagram
0347-top-k-frequent-elements
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0594-longest-harmonious-subsequence
0924-fair-candy-swap
1468-check-if-n-and-its-double-exist
1478-maximum-number-of-events-that-can-be-attended
1482-how-many-numbers-are-smaller-than-the-current-number
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1730-special-array-with-x-elements-greater-than-or-equal-x
1851-maximum-number-of-events-that-can-be-attended-ii
2180-maximum-number-of-tasks-you-can-assign
2204-find-subsequence-of-length-k-with-the-largest-sum
2215-finding-3-digit-even-numbers
2387-partition-array-such-that-maximum-difference-is-k
2479-meeting-rooms-iii
2689-rearranging-fruits
2699-count-the-number-of-fair-pairs
3241-divide-array-into-arrays-with-max-difference
3307-find-the-maximum-sum-of-node-values
3321-type-of-triangle
3360-minimum-deletions-to-make-string-k-special
3647-zero-array-transformation-iii

Counting

0169-majority-element
0229-majority-element-ii
0347-top-k-frequent-elements
0594-longest-harmonious-subsequence
1227-number-of-equivalent-domino-pairs
1510-find-lucky-integer-in-an-array
1635-number-of-good-pairs
1986-largest-color-value-in-a-directed-graph
2140-longest-subsequence-repeated-k-times
2237-longest-palindrome-by-concatenating-two-letter-words
3360-minimum-deletions-to-make-string-k-special
3629-total-characters-in-string-after-transformations-i
3630-total-characters-in-string-after-transformations-ii
3753-maximum-difference-between-even-and-odd-frequency-i
3754-maximum-manhattan-distance-after-k-changes

Matrix

0036-valid-sudoku
0054-spiral-matrix
0059-spiral-matrix-ii
0073-set-matrix-zeroes
0200-number-of-islands
0921-spiral-matrix-iii
0945-snakes-and-ladders
1476-count-negative-numbers-in-a-sorted-matrix
1791-richest-customer-wealth
3627-find-minimum-time-to-reach-last-room-i
3628-find-minimum-time-to-reach-last-room-ii

Counting Sort

1482-how-many-numbers-are-smaller-than-the-current-number

Enumeration

1656-count-good-triplets
2140-longest-subsequence-repeated-k-times
2170-count-number-of-maximum-bitwise-or-subsets
2202-sum-of-k-mirror-numbers
2215-finding-3-digit-even-numbers
3201-distribute-candies-among-children-ii
3683-find-the-lexicographically-largest-string-from-the-box-i
3741-reschedule-meetings-for-maximum-free-time-ii
3761-maximum-difference-between-even-and-odd-frequency-ii
3789-maximize-subarrays-after-removing-one-conflicting-pair

Divide and Conquer

0053-maximum-subarray
0169-majority-element
0347-top-k-frequent-elements

Sliding Window

0003-longest-substring-without-repeating-characters
0594-longest-harmonious-subsequence
0940-fruit-into-baskets
1813-maximum-erasure-value
2229-maximum-fruits-harvested-after-at-most-k-steps
2498-smallest-subarrays-with-maximum-bitwise-or
2527-count-subarrays-with-fixed-bounds
2626-count-the-number-of-good-subarrays
2856-count-complete-subarrays-in-an-array
3213-count-subarrays-where-max-element-appears-at-least-k-times
3743-reschedule-meetings-for-maximum-free-time-i
3761-maximum-difference-between-even-and-odd-frequency-ii

Number Theory

1372-check-if-it-is-a-good-array
2415-count-the-number-of-ideal-arrays

Binary Search

0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0069-sqrtx
0081-search-in-rotated-sorted-array-ii
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0278-first-bad-version
0349-intersection-of-two-arrays
0350-intersection-of-two-arrays-ii
0367-valid-perfect-square
0374-guess-number-higher-or-lower
0441-arranging-coins
0540-single-element-in-a-sorted-array
0745-find-smallest-letter-greater-than-target
0792-binary-search
0882-peak-index-in-a-mountain-array
0924-fair-candy-swap
1468-check-if-n-and-its-double-exist
1476-count-negative-numbers-in-a-sorted-matrix
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1646-kth-missing-positive-number
1730-special-array-with-x-elements-greater-than-or-equal-x
1851-maximum-number-of-events-that-can-be-attended-ii
2150-kth-smallest-product-of-two-sorted-arrays
2180-maximum-number-of-tasks-you-can-assign
2229-maximum-fruits-harvested-after-at-most-k-steps
2498-smallest-subarrays-with-maximum-bitwise-or
2699-count-the-number-of-fair-pairs
2720-minimize-the-maximum-difference-of-pairs

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0038-count-and-say
0049-group-anagrams
0125-valid-palindrome
0242-valid-anagram
0344-reverse-string
0868-push-dominoes
1058-lexicographically-smallest-equivalent-string
1302-delete-characters-to-make-fancy-string
1350-remove-sub-folders-from-the-filesystem
1818-maximum-score-from-removing-substrings
2079-delete-duplicate-folders-in-system
2140-longest-subsequence-repeated-k-times
2237-longest-palindrome-by-concatenating-two-letter-words
2260-divide-a-string-into-groups-of-size-k
2395-longest-binary-subsequence-less-than-or-equal-to-k
2520-using-a-robot-to-print-the-lexicographically-smallest-string
3142-longest-unequal-adjacent-groups-subsequence-ii
3143-longest-unequal-adjacent-groups-subsequence-i
3194-find-words-containing-character
3360-minimum-deletions-to-make-string-k-special
3396-valid-word
3445-lexicographically-minimum-string-after-removing-stars
3617-find-the-original-typed-string-i
3618-find-the-original-typed-string-ii
3629-total-characters-in-string-after-transformations-i
3630-total-characters-in-string-after-transformations-ii
3637-count-number-of-balanced-permutations
3683-find-the-lexicographically-largest-string-from-the-box-i
3753-maximum-difference-between-even-and-odd-frequency-i
3754-maximum-manhattan-distance-after-k-changes
3761-maximum-difference-between-even-and-odd-frequency-ii

Interactive

0278-first-bad-version
0374-guess-number-higher-or-lower

Greedy

0011-container-with-most-water
0135-candy
0797-rabbits-in-forest
1049-minimum-domino-rotations-for-equal-row
1478-maximum-number-of-events-that-can-be-attended
1529-max-difference-you-can-get-from-changing-an-integer
1818-maximum-score-from-removing-substrings
2140-longest-subsequence-repeated-k-times
2180-maximum-number-of-tasks-you-can-assign
2237-longest-palindrome-by-concatenating-two-letter-words
2387-partition-array-such-that-maximum-difference-is-k
2395-longest-binary-subsequence-less-than-or-equal-to-k
2520-using-a-robot-to-print-the-lexicographically-smallest-string
2689-rearranging-fruits
2704-maximum-difference-by-remapping-a-digit
2720-minimize-the-maximum-difference-of-pairs
3143-longest-unequal-adjacent-groups-subsequence-i
3171-minimum-equal-sum-of-two-arrays-after-replacing-zeros
3241-divide-array-into-arrays-with-max-difference
3307-find-the-maximum-sum-of-node-values
3360-minimum-deletions-to-make-string-k-special
3445-lexicographically-minimum-string-after-removing-stars
3647-zero-array-transformation-iii
3741-reschedule-meetings-for-maximum-free-time-ii
3743-reschedule-meetings-for-maximum-free-time-i
3788-maximum-unique-subarray-sum-after-deletion

Dynamic Programming

0005-longest-palindromic-substring
0053-maximum-subarray
0118-pascals-triangle
0121-best-time-to-buy-and-sell-stock
0806-domino-and-tromino-tiling
0868-push-dominoes
0934-bitwise-ors-of-subarrays
1851-maximum-number-of-events-that-can-be-attended-ii
1986-largest-color-value-in-a-directed-graph
2028-the-earliest-and-latest-rounds-where-players-compete
2061-painting-a-grid-with-three-different-colors
2267-minimum-difference-in-sums-after-removal-of-elements
2395-longest-binary-subsequence-less-than-or-equal-to-k
2415-count-the-number-of-ideal-arrays
3142-longest-unequal-adjacent-groups-subsequence-ii
3143-longest-unequal-adjacent-groups-subsequence-i
3307-find-the-maximum-sum-of-node-values
3490-find-the-maximum-length-of-valid-subsequence-i
3491-find-the-maximum-length-of-valid-subsequence-ii
3618-find-the-original-typed-string-ii
3629-total-characters-in-string-after-transformations-i
3630-total-characters-in-string-after-transformations-ii
3637-count-number-of-balanced-permutations

Combinatorics

2415-count-the-number-of-ideal-arrays
3201-distribute-candies-among-children-ii
3637-count-number-of-balanced-permutations
3682-count-the-number-of-arrays-with-k-matching-adjacent-elements

Queue

2180-maximum-number-of-tasks-you-can-assign
2527-count-subarrays-with-fixed-bounds

Monotonic Queue

2180-maximum-number-of-tasks-you-can-assign
2527-count-subarrays-with-fixed-bounds

Graph

1424-maximum-candies-you-can-get-from-boxes
1986-largest-color-value-in-a-directed-graph
2438-find-closest-node-to-given-two-nodes
3627-find-minimum-time-to-reach-last-room-i
3628-find-minimum-time-to-reach-last-room-ii

Heap (Priority Queue)

0347-top-k-frequent-elements
1478-maximum-number-of-events-that-can-be-attended
2204-find-subsequence-of-length-k-with-the-largest-sum
2267-minimum-difference-in-sums-after-removal-of-elements
2479-meeting-rooms-iii
3445-lexicographically-minimum-string-after-removing-stars
3627-find-minimum-time-to-reach-last-room-i
3628-find-minimum-time-to-reach-last-room-ii
3647-zero-array-transformation-iii

Shortest Path

3627-find-minimum-time-to-reach-last-room-i
3628-find-minimum-time-to-reach-last-room-ii

Bit Manipulation

0934-bitwise-ors-of-subarrays
2170-count-number-of-maximum-bitwise-or-subsets
2400-minimum-score-after-removals-on-a-tree
2498-smallest-subarrays-with-maximum-bitwise-or
2503-longest-subarray-with-maximum-bitwise-and
3307-find-the-maximum-sum-of-node-values
3600-find-the-k-th-character-in-string-game-i
3601-find-the-k-th-character-in-string-game-ii

Tree

0098-validate-binary-search-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree
1218-lowest-common-ancestor-of-deepest-leaves
2400-minimum-score-after-removals-on-a-tree
3307-find-the-maximum-sum-of-node-values
3633-maximize-the-number-of-target-nodes-after-connecting-trees-i
3645-maximize-the-number-of-target-nodes-after-connecting-trees-ii

Topological Sort

1986-largest-color-value-in-a-directed-graph

Memoization

1986-largest-color-value-in-a-directed-graph
2028-the-earliest-and-latest-rounds-where-players-compete
2395-longest-binary-subsequence-less-than-or-equal-to-k

Depth-First Search

0098-validate-binary-search-tree
0101-symmetric-tree
0104-maximum-depth-of-binary-tree
0200-number-of-islands
0386-lexicographical-numbers
1218-lowest-common-ancestor-of-deepest-leaves
1350-remove-sub-folders-from-the-filesystem
2400-minimum-score-after-removals-on-a-tree
2438-find-closest-node-to-given-two-nodes
3633-maximize-the-number-of-target-nodes-after-connecting-trees-i
3645-maximize-the-number-of-target-nodes-after-connecting-trees-ii

Breadth-First Search

0101-symmetric-tree
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree
0200-number-of-islands
0945-snakes-and-ladders
1218-lowest-common-ancestor-of-deepest-leaves
1424-maximum-candies-you-can-get-from-boxes
3633-maximize-the-number-of-target-nodes-after-connecting-trees-i
3645-maximize-the-number-of-target-nodes-after-connecting-trees-ii

Union Find

0128-longest-consecutive-sequence
0200-number-of-islands
1058-lexicographically-smallest-equivalent-string

Stack

1818-maximum-score-from-removing-substrings
2520-using-a-robot-to-print-the-lexicographically-smallest-string
3445-lexicographically-minimum-string-after-removing-stars

Trie

0386-lexicographical-numbers
0440-k-th-smallest-in-lexicographical-order
1350-remove-sub-folders-from-the-filesystem
2079-delete-duplicate-folders-in-system

Backtracking

2140-longest-subsequence-repeated-k-times
2170-count-number-of-maximum-bitwise-or-subsets

Recursion

0206-reverse-linked-list
3600-find-the-k-th-character-in-string-game-i
3601-find-the-k-th-character-in-string-game-ii

Design

1995-finding-pairs-with-a-certain-sum

Linked List

0019-remove-nth-node-from-end-of-list
0141-linked-list-cycle
0160-intersection-of-two-linked-lists
0206-reverse-linked-list
1411-convert-binary-number-in-a-linked-list-to-integer

Hash Function

2079-delete-duplicate-folders-in-system

Binary Tree

0098-validate-binary-search-tree
0101-symmetric-tree
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree
1218-lowest-common-ancestor-of-deepest-leaves

Binary Search Tree

0098-validate-binary-search-tree

Segment Tree

3789-maximize-subarrays-after-removing-one-conflicting-pair

Brainteaser

2503-longest-subarray-with-maximum-bitwise-and

Bucket Sort

0347-top-k-frequent-elements

Quickselect

0347-top-k-frequent-elements