leetcode

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

LeetCode Topics

Array

0001-two-sum
0014-longest-common-prefix
0016-3sum-closest
0018-4sum
0026-remove-duplicates-from-sorted-array
0027-remove-element
0031-next-permutation
0039-combination-sum
0040-combination-sum-ii
0059-spiral-matrix-ii
0066-plus-one
0088-merge-sorted-array
0108-convert-sorted-array-to-binary-search-tree
0119-pascals-triangle-ii
0121-best-time-to-buy-and-sell-stock
0130-surrounded-regions
0150-evaluate-reverse-polish-notation
0169-majority-element
0217-contains-duplicate
0448-find-all-numbers-disappeared-in-an-array
0455-assign-cookies
0485-max-consecutive-ones
0496-next-greater-element-i
0500-keyboard-row
0561-array-partition
0566-reshape-the-matrix
0594-longest-harmonious-subsequence
0628-maximum-product-of-three-numbers
0636-exclusive-time-of-functions
0645-set-mismatch
0733-flood-fill
0832-flipping-an-image
0835-image-overlap
0877-stone-game
0914-x-of-a-kind-in-a-deck-of-cards
1030-matrix-cells-in-distance-order
1140-stone-game-ii
1331-rank-transform-of-an-array
1365-how-many-numbers-are-smaller-than-the-current-number
1406-stone-game-iii
1441-build-an-array-with-stack-operations
1470-shuffle-the-array
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1512-number-of-good-pairs
1572-matrix-diagonal-sum
1658-minimum-operations-to-reduce-x-to-zero
1807-evaluate-the-bracket-pairs-of-a-string
1840-maximum-building-height
1929-concatenation-of-array
1979-find-greatest-common-divisor-of-array
2267-check-if-there-is-a-valid-parentheses-string-path
2333-minimum-sum-of-squared-difference
2500-delete-greatest-value-in-each-row
2812-find-the-safest-path-in-a-grid
2897-apply-operations-on-array-to-maximize-sum-of-squares
2958-length-of-longest-subarray-with-at-most-k-frequency
2996-smallest-missing-integer-greater-than-sequential-prefix-sum
3033-modify-the-matrix
3312-sorted-gcd-pair-queries
3336-find-the-number-of-subsequences-with-equal-gcd
3414-maximum-score-of-non-overlapping-intervals
3483-unique-3-digit-even-numbers
3524-find-x-value-of-array-i
3525-find-x-value-of-array-ii
3550-smallest-index-with-digit-sum-equal-to-index
3568-minimum-moves-to-clean-the-classroom
3718-smallest-missing-multiple-of-k
3727-maximum-alternating-sum-of-squares
3731-find-missing-elements
3867-sum-of-gcd-of-formed-pairs
3875-construct-uniform-parity-array-i
3876-construct-uniform-parity-array-ii
3903-smallest-stable-index-i
3904-smallest-stable-index-ii

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0013-roman-to-integer
0017-letter-combinations-of-a-phone-number
0141-linked-list-cycle
0169-majority-element
0202-happy-number
0217-contains-duplicate
0383-ransom-note
0448-find-all-numbers-disappeared-in-an-array
0496-next-greater-element-i
0500-keyboard-row
0594-longest-harmonious-subsequence
0645-set-mismatch
0653-two-sum-iv-input-is-a-bst
0914-x-of-a-kind-in-a-deck-of-cards
1096-brace-expansion-ii
1331-rank-transform-of-an-array
1365-how-many-numbers-are-smaller-than-the-current-number
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1512-number-of-good-pairs
1520-maximum-number-of-non-overlapping-substrings
1658-minimum-operations-to-reduce-x-to-zero
1807-evaluate-the-bracket-pairs-of-a-string
2897-apply-operations-on-array-to-maximize-sum-of-squares
2958-length-of-longest-subarray-with-at-most-k-frequency
2996-smallest-missing-integer-greater-than-sequential-prefix-sum
3312-sorted-gcd-pair-queries
3483-unique-3-digit-even-numbers
3568-minimum-moves-to-clean-the-classroom
3718-smallest-missing-multiple-of-k
3731-find-missing-elements

Math

0009-palindrome-number
0013-roman-to-integer
0043-multiply-strings
0050-powx-n
0066-plus-one
0067-add-binary
0069-sqrtx
0070-climbing-stairs
0089-gray-code
0150-evaluate-reverse-polish-notation
0168-excel-sheet-column-title
0171-excel-sheet-column-number
0202-happy-number
0224-basic-calculator
0231-power-of-two
0258-add-digits
0292-nim-game
0342-power-of-four
0367-valid-perfect-square
0412-fizz-buzz
0415-add-strings
0628-maximum-product-of-three-numbers
0836-rectangle-overlap
0877-stone-game
0914-x-of-a-kind-in-a-deck-of-cards
1025-divisor-game
1030-matrix-cells-in-distance-order
1140-stone-game-ii
1401-circle-and-rectangle-overlapping
1406-stone-game-iii
1510-stone-game-iv
1512-number-of-good-pairs
1621-number-of-sets-of-k-non-overlapping-line-segments
1840-maximum-building-height
1979-find-greatest-common-divisor-of-array
3312-sorted-gcd-pair-queries
3336-find-the-number-of-subsequences-with-equal-gcd
3524-find-x-value-of-array-i
3525-find-x-value-of-array-ii
3550-smallest-index-with-digit-sum-equal-to-index
3658-gcd-of-odd-and-even-sums
3723-maximize-sum-of-squares-of-digits
3867-sum-of-gcd-of-formed-pairs
3870-count-commas-in-range
3871-count-commas-in-range-ii
3875-construct-uniform-parity-array-i
3876-construct-uniform-parity-array-ii

Binary Search

0069-sqrtx
0367-valid-perfect-square
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1658-minimum-operations-to-reduce-x-to-zero
2333-minimum-sum-of-squared-difference
2812-find-the-safest-path-in-a-grid
3312-sorted-gcd-pair-queries
3414-maximum-score-of-non-overlapping-intervals

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0006-zigzag-conversion
0013-roman-to-integer
0014-longest-common-prefix
0017-letter-combinations-of-a-phone-number
0020-valid-parentheses
0022-generate-parentheses
0032-longest-valid-parentheses
0043-multiply-strings
0058-length-of-last-word
0067-add-binary
0091-decode-ways
0115-distinct-subsequences
0125-valid-palindrome
0168-excel-sheet-column-title
0171-excel-sheet-column-number
0224-basic-calculator
0383-ransom-note
0412-fizz-buzz
0415-add-strings
0500-keyboard-row
0521-longest-uncommon-subsequence-i
0678-valid-parenthesis-string
0796-rotate-string
0856-score-of-parentheses
0921-minimum-add-to-make-parentheses-valid
0940-distinct-subsequences-ii
1021-remove-outermost-parentheses
1096-brace-expansion-ii
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses
1221-split-a-string-in-balanced-strings
1520-maximum-number-of-non-overlapping-substrings
1541-minimum-insertions-to-balance-a-parentheses-string
1614-maximum-nesting-depth-of-the-parentheses
1807-evaluate-the-bracket-pairs-of-a-string
2472-maximum-number-of-non-overlapping-palindrome-substrings
3498-reverse-degree-of-a-string

Stack

0020-valid-parentheses
0032-longest-valid-parentheses
0094-binary-tree-inorder-traversal
0150-evaluate-reverse-polish-notation
0224-basic-calculator
0496-next-greater-element-i
0636-exclusive-time-of-functions
0678-valid-parenthesis-string
0856-score-of-parentheses
0897-increasing-order-search-tree
0921-minimum-add-to-make-parentheses-valid
1021-remove-outermost-parentheses
1096-brace-expansion-ii
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses
1441-build-an-array-with-stack-operations
1541-minimum-insertions-to-balance-a-parentheses-string
1614-maximum-nesting-depth-of-the-parentheses

Two Pointers

0005-longest-palindromic-substring
0016-3sum-closest
0018-4sum
0026-remove-duplicates-from-sorted-array
0027-remove-element
0031-next-permutation
0061-rotate-list
0088-merge-sorted-array
0125-valid-palindrome
0141-linked-list-cycle
0202-happy-number
0455-assign-cookies
0653-two-sum-iv-input-is-a-bst
0832-flipping-an-image
2472-maximum-number-of-non-overlapping-palindrome-substrings
3867-sum-of-gcd-of-formed-pairs

Bit Manipulation

0067-add-binary
0089-gray-code
0191-number-of-1-bits
0231-power-of-two
0342-power-of-four
0401-binary-watch
0645-set-mismatch
0832-flipping-an-image
2897-apply-operations-on-array-to-maximize-sum-of-squares
3568-minimum-moves-to-clean-the-classroom

Recursion

0021-merge-two-sorted-lists
0024-swap-nodes-in-pairs
0050-powx-n
0206-reverse-linked-list
0224-basic-calculator
0231-power-of-two
0342-power-of-four
3483-unique-3-digit-even-numbers

Simulation

0043-multiply-strings
0059-spiral-matrix-ii
0067-add-binary
0258-add-digits
0412-fizz-buzz
0415-add-strings
0566-reshape-the-matrix
0832-flipping-an-image
1441-build-an-array-with-stack-operations
1929-concatenation-of-array
2500-delete-greatest-value-in-each-row
3498-reverse-degree-of-a-string
3867-sum-of-gcd-of-formed-pairs

Number Theory

0258-add-digits
0914-x-of-a-kind-in-a-deck-of-cards
1979-find-greatest-common-divisor-of-array
3312-sorted-gcd-pair-queries
3336-find-the-number-of-subsequences-with-equal-gcd
3658-gcd-of-odd-and-even-sums
3867-sum-of-gcd-of-formed-pairs

Dynamic Programming

0005-longest-palindromic-substring
0022-generate-parentheses
0032-longest-valid-parentheses
0070-climbing-stairs
0091-decode-ways
0115-distinct-subsequences
0119-pascals-triangle-ii
0121-best-time-to-buy-and-sell-stock
0678-valid-parenthesis-string
0877-stone-game
0940-distinct-subsequences-ii
1025-divisor-game
1140-stone-game-ii
1406-stone-game-iii
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1510-stone-game-iv
1621-number-of-sets-of-k-non-overlapping-line-segments
2267-check-if-there-is-a-valid-parentheses-string-path
2472-maximum-number-of-non-overlapping-palindrome-substrings
3336-find-the-number-of-subsequences-with-equal-gcd
3414-maximum-score-of-non-overlapping-intervals
3524-find-x-value-of-array-i

Linked List

0021-merge-two-sorted-lists
0024-swap-nodes-in-pairs
0061-rotate-list
0083-remove-duplicates-from-sorted-list
0116-populating-next-right-pointers-in-each-node
0141-linked-list-cycle
0206-reverse-linked-list

Depth-First Search

0094-binary-tree-inorder-traversal
0100-same-tree
0101-symmetric-tree
0110-balanced-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0130-surrounded-regions
0653-two-sum-iv-input-is-a-bst
0733-flood-fill
0897-increasing-order-search-tree
0938-range-sum-of-bst
2265-count-nodes-equal-to-average-of-subtree
2685-count-the-number-of-complete-components

Breadth-First Search

0100-same-tree
0101-symmetric-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0130-surrounded-regions
0653-two-sum-iv-input-is-a-bst
0733-flood-fill
1096-brace-expansion-ii
2685-count-the-number-of-complete-components
2812-find-the-safest-path-in-a-grid
3568-minimum-moves-to-clean-the-classroom

Union-Find

0130-surrounded-regions
2685-count-the-number-of-complete-components
2812-find-the-safest-path-in-a-grid

Graph Theory

2685-count-the-number-of-complete-components

Sorting

0016-3sum-closest
0018-4sum
0088-merge-sorted-array
0169-majority-element
0217-contains-duplicate
0455-assign-cookies
0561-array-partition
0594-longest-harmonious-subsequence
0628-maximum-product-of-three-numbers
0645-set-mismatch
1030-matrix-cells-in-distance-order
1096-brace-expansion-ii
1331-rank-transform-of-an-array
1365-how-many-numbers-are-smaller-than-the-current-number
1520-maximum-number-of-non-overlapping-substrings
1840-maximum-building-height
2333-minimum-sum-of-squared-difference
2500-delete-greatest-value-in-each-row
2996-smallest-missing-integer-greater-than-sequential-prefix-sum
3414-maximum-score-of-non-overlapping-intervals
3727-maximum-alternating-sum-of-squares
3731-find-missing-elements
3867-sum-of-gcd-of-formed-pairs

Tree

0094-binary-tree-inorder-traversal
0100-same-tree
0101-symmetric-tree
0108-convert-sorted-array-to-binary-search-tree
0110-balanced-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0653-two-sum-iv-input-is-a-bst
0897-increasing-order-search-tree
0938-range-sum-of-bst
2265-count-nodes-equal-to-average-of-subtree

Binary Tree

0094-binary-tree-inorder-traversal
0100-same-tree
0101-symmetric-tree
0108-convert-sorted-array-to-binary-search-tree
0110-balanced-binary-tree
0112-path-sum
0116-populating-next-right-pointers-in-each-node
0653-two-sum-iv-input-is-a-bst
0897-increasing-order-search-tree
0938-range-sum-of-bst
2265-count-nodes-equal-to-average-of-subtree

Enumeration

1291-sequential-digits
3483-unique-3-digit-even-numbers

Backtracking

0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0039-combination-sum
0040-combination-sum-ii
0089-gray-code
0401-binary-watch
1096-brace-expansion-ii

Combinatorics

1621-number-of-sets-of-k-non-overlapping-line-segments
3312-sorted-gcd-pair-queries

Counting

0169-majority-element
0383-ransom-note
0594-longest-harmonious-subsequence
0914-x-of-a-kind-in-a-deck-of-cards
1221-split-a-string-in-balanced-strings
1512-number-of-good-pairs
3312-sorted-gcd-pair-queries

Prefix Sum

1140-stone-game-ii
1621-number-of-sets-of-k-non-overlapping-line-segments
1658-minimum-operations-to-reduce-x-to-zero
3312-sorted-gcd-pair-queries
3903-smallest-stable-index-i
3904-smallest-stable-index-ii

Trie

0014-longest-common-prefix

Game Theory

0292-nim-game
0877-stone-game
1025-divisor-game
1140-stone-game-ii
1406-stone-game-iii
1510-stone-game-iv

Minimax

0292-nim-game
1140-stone-game-ii
1406-stone-game-iii
1510-stone-game-iv

Zero-Sum Game

1140-stone-game-ii
1406-stone-game-iii
1510-stone-game-iv

Bracket Sequences

0020-valid-parentheses
0022-generate-parentheses
0032-longest-valid-parentheses
0678-valid-parenthesis-string
0856-score-of-parentheses
0921-minimum-add-to-make-parentheses-valid
1021-remove-outermost-parentheses
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses
1541-minimum-insertions-to-balance-a-parentheses-string
1614-maximum-nesting-depth-of-the-parentheses
2267-check-if-there-is-a-valid-parentheses-string-path

Manacher

0005-longest-palindromic-substring

Divide and Conquer

0108-convert-sorted-array-to-binary-search-tree
0169-majority-element
0191-number-of-1-bits

Binary Search Tree

0108-convert-sorted-array-to-binary-search-tree
0653-two-sum-iv-input-is-a-bst
0897-increasing-order-search-tree
0938-range-sum-of-bst

Database

0175-combine-two-tables
0176-second-highest-salary
0181-employees-earning-more-than-their-managers
0182-duplicate-emails
0183-customers-who-never-order
0185-department-top-three-salaries
0196-delete-duplicate-emails
0197-rising-temperature
0511-game-play-analysis-i
0595-big-countries
0608-tree-node
1527-patients-with-a-condition

Boyer–Moore Majority Vote Algorithm

0169-majority-element

Memoization

0070-climbing-stairs

Brainteaser

0292-nim-game
1025-divisor-game

Nim Game

0292-nim-game
1510-stone-game-iv

Impartial Game

0292-nim-game
1025-divisor-game

Euclidean Algorithm

0914-x-of-a-kind-in-a-deck-of-cards
3336-find-the-number-of-subsequences-with-equal-gcd

Greatest Common Divisor

0914-x-of-a-kind-in-a-deck-of-cards
3336-find-the-number-of-subsequences-with-equal-gcd

Sprague–Grundy Theorem

1510-stone-game-iv

Sliding Window

0003-longest-substring-without-repeating-characters
0594-longest-harmonious-subsequence
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1658-minimum-operations-to-reduce-x-to-zero
2958-length-of-longest-subarray-with-at-most-k-frequency

Greedy

0455-assign-cookies
0561-array-partition
0678-valid-parenthesis-string
0921-minimum-add-to-make-parentheses-valid
1221-split-a-string-in-balanced-strings
1520-maximum-number-of-non-overlapping-substrings
1541-minimum-insertions-to-balance-a-parentheses-string
2333-minimum-sum-of-squared-difference
2472-maximum-number-of-non-overlapping-palindrome-substrings
2897-apply-operations-on-array-to-maximize-sum-of-squares
3723-maximize-sum-of-squares-of-digits
3727-maximum-alternating-sum-of-squares

Quicksort

0455-assign-cookies

Floyd's Cycle Finding Algorithm

0141-linked-list-cycle
0202-happy-number

Monotonic Stack

0496-next-greater-element-i

Matrix

0059-spiral-matrix-ii
0130-surrounded-regions
0566-reshape-the-matrix
0733-flood-fill
0832-flipping-an-image
0835-image-overlap
1030-matrix-cells-in-distance-order
1572-matrix-diagonal-sum
2267-check-if-there-is-a-valid-parentheses-string-path
2500-delete-greatest-value-in-each-row
2812-find-the-safest-path-in-a-grid
3033-modify-the-matrix
3568-minimum-moves-to-clean-the-classroom

Counting Sort

0561-array-partition
1365-how-many-numbers-are-smaller-than-the-current-number

Geometry

0836-rectangle-overlap
1030-matrix-cells-in-distance-order
1401-circle-and-rectangle-overlapping

Heap (Priority Queue)

2333-minimum-sum-of-squared-difference
2500-delete-greatest-value-in-each-row
2812-find-the-safest-path-in-a-grid

String Matching

0796-rotate-string

Segment Tree

3525-find-x-value-of-array-ii