LeetCode

A collection of LeetCode questions to ace the coding interview! - Created using LeetHub v2

LeetCode Topics

Array

0001-two-sum
0004-median-of-two-sorted-arrays
0011-container-with-most-water
0015-3sum
0026-remove-duplicates-from-sorted-array
0027-remove-element
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0036-valid-sudoku
0039-combination-sum
0040-combination-sum-ii
0042-trapping-rain-water
0046-permutations
0047-permutations-ii
0048-rotate-image
0049-group-anagrams
0053-maximum-subarray
0055-jump-game
0056-merge-intervals
0059-spiral-matrix-ii
0066-plus-one
0074-search-a-2d-matrix
0075-sort-colors
0078-subsets
0088-merge-sorted-array
0090-subsets-ii
0121-best-time-to-buy-and-sell-stock
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
0179-largest-number
0198-house-robber
0200-number-of-islands
0209-minimum-size-subarray-sum
0213-house-robber-ii
0217-contains-duplicate
0238-product-of-array-except-self
0239-sliding-window-maximum
0283-move-zeroes
0287-find-the-duplicate-number
0300-longest-increasing-subsequence
0303-range-sum-query-immutable
0322-coin-change
0347-top-k-frequent-elements
0380-insert-delete-getrandom-o1
0414-third-maximum-number
0417-pacific-atlantic-water-flow
0435-non-overlapping-intervals
0448-find-all-numbers-disappeared-in-an-array
0454-4sum-ii
0473-matchsticks-to-square
0475-heaters
0485-max-consecutive-ones
0496-next-greater-element-i
0498-diagonal-traverse
0532-k-diff-pairs-in-an-array
0542-01-matrix
0566-reshape-the-matrix
0695-max-area-of-island
0704-binary-search
0721-accounts-merge
0724-find-pivot-index
0733-flood-fill
0739-daily-temperatures
0746-min-cost-climbing-stairs
0748-largest-number-at-least-twice-of-others
0777-toeplitz-matrix
0792-binary-search
0853-car-fleet
0860-design-circular-queue
0875-koko-eating-bananas
0898-transpose-matrix
0941-sort-array-by-parity
0948-sort-an-array
0959-3sum-with-multiplicity
0978-valid-mountain-array
0987-reveal-cards-in-increasing-order
0991-array-of-doubled-pairs
0994-rotting-oranges
1009-pancake-sorting
1014-k-closest-points-to-origin
1046-last-stone-weight
1055-pairs-of-songs-with-total-durations-divisible-by-60
1137-height-checker
1168-duplicate-zeros
1231-replace-elements-with-greatest-element-on-right-side
1421-find-numbers-with-even-number-of-digits
1605-minimum-number-of-days-to-make-m-bouquets
1848-sum-of-unique-elements
1966-frequency-of-the-most-frequent-element
1985-maximum-subarray-min-product
2237-longest-palindrome-by-concatenating-two-letter-words
2454-largest-local-values-in-a-matrix
3420-find-occurrences-of-an-element-in-an-array
3434-find-the-number-of-distinct-colors-among-the-balls

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
0076-minimum-window-substring
0127-word-ladder
0128-longest-consecutive-sequence
0133-clone-graph
0138-copy-list-with-random-pointer
0139-word-break
0141-linked-list-cycle
0142-linked-list-cycle-ii
0146-lru-cache
0160-intersection-of-two-linked-lists
0169-majority-element
0205-isomorphic-strings
0217-contains-duplicate
0242-valid-anagram
0347-top-k-frequent-elements
0380-insert-delete-getrandom-o1
0383-ransom-note
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0448-find-all-numbers-disappeared-in-an-array
0451-sort-characters-by-frequency
0454-4sum-ii
0496-next-greater-element-i
0532-k-diff-pairs-in-an-array
0567-permutation-in-string
0721-accounts-merge
0959-3sum-with-multiplicity
0981-time-based-key-value-store
0991-array-of-doubled-pairs
1055-pairs-of-songs-with-total-durations-divisible-by-60
1848-sum-of-unique-elements
2237-longest-palindrome-by-concatenating-two-letter-words
3420-find-occurrences-of-an-element-in-an-array
3434-find-the-number-of-distinct-colors-among-the-balls

Two Pointers

0005-longest-palindromic-substring
0011-container-with-most-water
0015-3sum
0019-remove-nth-node-from-end-of-list
0026-remove-duplicates-from-sorted-array
0027-remove-element
0042-trapping-rain-water
0075-sort-colors
0088-merge-sorted-array
0125-valid-palindrome
0141-linked-list-cycle
0142-linked-list-cycle-ii
0143-reorder-list
0148-sort-list
0160-intersection-of-two-linked-lists
0167-two-sum-ii-input-array-is-sorted
0234-palindrome-linked-list
0283-move-zeroes
0287-find-the-duplicate-number
0344-reverse-string
0475-heaters
0532-k-diff-pairs-in-an-array
0567-permutation-in-string
0647-palindromic-substrings
0908-middle-of-the-linked-list
0941-sort-array-by-parity
0959-3sum-with-multiplicity
1009-pancake-sorting
1168-duplicate-zeros

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0013-roman-to-integer
0017-letter-combinations-of-a-phone-number
0020-valid-parentheses
0049-group-anagrams
0076-minimum-window-substring
0091-decode-ways
0125-valid-palindrome
0127-word-ladder
0131-palindrome-partitioning
0139-word-break
0179-largest-number
0205-isomorphic-strings
0227-basic-calculator-ii
0242-valid-anagram
0297-serialize-and-deserialize-binary-tree
0344-reverse-string
0383-ransom-note
0394-decode-string
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0451-sort-characters-by-frequency
0567-permutation-in-string
0647-palindromic-substrings
0721-accounts-merge
0981-time-based-key-value-store
2237-longest-palindrome-by-concatenating-two-letter-words

Sorting

0015-3sum
0047-permutations-ii
0049-group-anagrams
0056-merge-intervals
0075-sort-colors
0088-merge-sorted-array
0148-sort-list
0169-majority-element
0179-largest-number
0217-contains-duplicate
0242-valid-anagram
0347-top-k-frequent-elements
0414-third-maximum-number
0435-non-overlapping-intervals
0451-sort-characters-by-frequency
0475-heaters
0532-k-diff-pairs-in-an-array
0721-accounts-merge
0748-largest-number-at-least-twice-of-others
0853-car-fleet
0941-sort-array-by-parity
0948-sort-an-array
0959-3sum-with-multiplicity
0987-reveal-cards-in-increasing-order
0991-array-of-doubled-pairs
1009-pancake-sorting
1014-k-closest-points-to-origin
1137-height-checker
1966-frequency-of-the-most-frequent-element

Divide and Conquer

0004-median-of-two-sorted-arrays
0023-merge-k-sorted-lists
0053-maximum-subarray
0109-convert-sorted-list-to-binary-search-tree
0148-sort-list
0169-majority-element
0347-top-k-frequent-elements
0948-sort-an-array
1014-k-closest-points-to-origin

Counting

0169-majority-element
0347-top-k-frequent-elements
0383-ransom-note
0451-sort-characters-by-frequency
0959-3sum-with-multiplicity
1055-pairs-of-songs-with-total-durations-divisible-by-60
1848-sum-of-unique-elements
2237-longest-palindrome-by-concatenating-two-letter-words

Dynamic Programming

0005-longest-palindromic-substring
0042-trapping-rain-water
0053-maximum-subarray
0055-jump-game
0070-climbing-stairs
0091-decode-ways
0121-best-time-to-buy-and-sell-stock
0124-binary-tree-maximum-path-sum
0131-palindrome-partitioning
0139-word-break
0152-maximum-product-subarray
0198-house-robber
0213-house-robber-ii
0300-longest-increasing-subsequence
0322-coin-change
0435-non-overlapping-intervals
0473-matchsticks-to-square
0542-01-matrix
0647-palindromic-substrings
0746-min-cost-climbing-stairs
1013-fibonacci-number

Math

0002-add-two-numbers
0013-roman-to-integer
0048-rotate-image
0050-powx-n
0066-plus-one
0069-sqrtx
0070-climbing-stairs
0150-evaluate-reverse-polish-notation
0227-basic-calculator-ii
0380-insert-delete-getrandom-o1
0441-arranging-coins
1013-fibonacci-number
1014-k-closest-points-to-origin
1421-find-numbers-with-even-number-of-digits

Linked List

0002-add-two-numbers
0019-remove-nth-node-from-end-of-list
0021-merge-two-sorted-lists
0023-merge-k-sorted-lists
0024-swap-nodes-in-pairs
0025-reverse-nodes-in-k-group
0083-remove-duplicates-from-sorted-list
0109-convert-sorted-list-to-binary-search-tree
0138-copy-list-with-random-pointer
0141-linked-list-cycle
0142-linked-list-cycle-ii
0143-reorder-list
0146-lru-cache
0148-sort-list
0160-intersection-of-two-linked-lists
0203-remove-linked-list-elements
0206-reverse-linked-list
0234-palindrome-linked-list
0328-odd-even-linked-list
0838-design-linked-list
0860-design-circular-queue
0908-middle-of-the-linked-list

Stack

0020-valid-parentheses
0042-trapping-rain-water
0143-reorder-list
0150-evaluate-reverse-polish-notation
0155-min-stack
0225-implement-stack-using-queues
0227-basic-calculator-ii
0232-implement-queue-using-stacks
0234-palindrome-linked-list
0394-decode-string
0496-next-greater-element-i
0739-daily-temperatures
0853-car-fleet
1985-maximum-subarray-min-product

Recursion

0002-add-two-numbers
0021-merge-two-sorted-lists
0024-swap-nodes-in-pairs
0025-reverse-nodes-in-k-group
0050-powx-n
0143-reorder-list
0203-remove-linked-list-elements
0206-reverse-linked-list
0234-palindrome-linked-list
0394-decode-string
1013-fibonacci-number

Binary Search

0004-median-of-two-sorted-arrays
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0069-sqrtx
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
0287-find-the-duplicate-number
0300-longest-increasing-subsequence
0441-arranging-coins
0475-heaters
0532-k-diff-pairs-in-an-array
0704-binary-search
0792-binary-search
0875-koko-eating-bananas
0981-time-based-key-value-store
1605-minimum-number-of-days-to-make-m-bouquets
1966-frequency-of-the-most-frequent-element

Design

0146-lru-cache
0155-min-stack
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0297-serialize-and-deserialize-binary-tree
0303-range-sum-query-immutable
0380-insert-delete-getrandom-o1
0703-kth-largest-element-in-a-stream
0838-design-linked-list
0860-design-circular-queue
0969-number-of-recent-calls
0981-time-based-key-value-store

Queue

0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0239-sliding-window-maximum
0860-design-circular-queue
0969-number-of-recent-calls
0987-reveal-cards-in-increasing-order

Prefix Sum

0209-minimum-size-subarray-sum
0238-product-of-array-except-self
0303-range-sum-query-immutable
0724-find-pivot-index
1966-frequency-of-the-most-frequent-element
1985-maximum-subarray-min-product

Memoization

0070-climbing-stairs
0139-word-break
1013-fibonacci-number

Counting Sort

0948-sort-an-array
1137-height-checker

Sliding Window

0003-longest-substring-without-repeating-characters
0076-minimum-window-substring
0209-minimum-size-subarray-sum
0239-sliding-window-maximum
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0567-permutation-in-string
1966-frequency-of-the-most-frequent-element

Greedy

0011-container-with-most-water
0055-jump-game
0179-largest-number
0435-non-overlapping-intervals
0991-array-of-doubled-pairs
1009-pancake-sorting
1966-frequency-of-the-most-frequent-element
2237-longest-palindrome-by-concatenating-two-letter-words

Monotonic Stack

0042-trapping-rain-water
0496-next-greater-element-i
0739-daily-temperatures
0853-car-fleet
1985-maximum-subarray-min-product

Randomized

0380-insert-delete-getrandom-o1

Doubly-Linked List

0146-lru-cache

Backtracking

0017-letter-combinations-of-a-phone-number
0039-combination-sum
0040-combination-sum-ii
0046-permutations
0047-permutations-ii
0077-combinations
0078-subsets
0090-subsets-ii
0131-palindrome-partitioning
0473-matchsticks-to-square

Bit Manipulation

0078-subsets
0090-subsets-ii
0287-find-the-duplicate-number
0473-matchsticks-to-square

Matrix

0036-valid-sudoku
0048-rotate-image
0059-spiral-matrix-ii
0074-search-a-2d-matrix
0130-surrounded-regions
0200-number-of-islands
0417-pacific-atlantic-water-flow
0498-diagonal-traverse
0542-01-matrix
0566-reshape-the-matrix
0695-max-area-of-island
0733-flood-fill
0777-toeplitz-matrix
0898-transpose-matrix
0994-rotting-oranges
2454-largest-local-values-in-a-matrix

Simulation

0059-spiral-matrix-ii
0498-diagonal-traverse
0566-reshape-the-matrix
0898-transpose-matrix
0987-reveal-cards-in-increasing-order
3434-find-the-number-of-distinct-colors-among-the-balls

Data Stream

0703-kth-largest-element-in-a-stream
0969-number-of-recent-calls

Heap (Priority Queue)

0023-merge-k-sorted-lists
0239-sliding-window-maximum
0347-top-k-frequent-elements
0451-sort-characters-by-frequency
0703-kth-largest-element-in-a-stream
0948-sort-an-array
1014-k-closest-points-to-origin
1046-last-stone-weight

Monotonic Queue

0239-sliding-window-maximum

Bitmask

0473-matchsticks-to-square

Interactive

0278-first-bad-version

Merge Sort

0023-merge-k-sorted-lists
0148-sort-list
0948-sort-an-array

Bucket Sort

0347-top-k-frequent-elements
0451-sort-characters-by-frequency
0948-sort-an-array

Radix Sort

0948-sort-an-array

Tree

0098-validate-binary-search-tree
0100-same-tree
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree
0124-binary-tree-maximum-path-sum
0199-binary-tree-right-side-view
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0297-serialize-and-deserialize-binary-tree
0543-diameter-of-binary-tree
0572-subtree-of-another-tree
0703-kth-largest-element-in-a-stream

Depth-First Search

0098-validate-binary-search-tree
0100-same-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
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
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0297-serialize-and-deserialize-binary-tree
0417-pacific-atlantic-water-flow
0543-diameter-of-binary-tree
0572-subtree-of-another-tree
0695-max-area-of-island
0721-accounts-merge
0733-flood-fill

Binary Tree

0098-validate-binary-search-tree
0100-same-tree
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree
0124-binary-tree-maximum-path-sum
0199-binary-tree-right-side-view
0226-invert-binary-tree
0230-kth-smallest-element-in-a-bst
0297-serialize-and-deserialize-binary-tree
0543-diameter-of-binary-tree
0572-subtree-of-another-tree
0703-kth-largest-element-in-a-stream

Quickselect

0347-top-k-frequent-elements
1014-k-closest-points-to-origin

Geometry

1014-k-closest-points-to-origin

Binary Search Tree

0098-validate-binary-search-tree
0109-convert-sorted-list-to-binary-search-tree
0230-kth-smallest-element-in-a-bst
0703-kth-largest-element-in-a-stream

Breadth-First Search

0100-same-tree
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree
0127-word-ladder
0130-surrounded-regions
0133-clone-graph
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0226-invert-binary-tree
0297-serialize-and-deserialize-binary-tree
0322-coin-change
0417-pacific-atlantic-water-flow
0542-01-matrix
0695-max-area-of-island
0721-accounts-merge
0733-flood-fill
0994-rotting-oranges

Graph

0133-clone-graph
0207-course-schedule

Union Find

0200-number-of-islands
0721-accounts-merge

Topological Sort

0207-course-schedule

Union-Find

0128-longest-consecutive-sequence
0130-surrounded-regions
0200-number-of-islands
0695-max-area-of-island

String Matching

0572-subtree-of-another-tree

Hash Function

0572-subtree-of-another-tree

Trie

0139-word-break

Graph Theory

0133-clone-graph
0207-course-schedule