LeetCode-Solution

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

LeetCode Topics

Tree

0094-binary-tree-inorder-traversal
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-binary-search-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
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0222-count-complete-tree-nodes
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0450-delete-node-in-a-bst
0662-maximum-width-of-binary-tree
0700-search-in-a-binary-search-tree
0701-insert-into-a-binary-search-tree
0863-all-nodes-distance-k-in-binary-tree
0872-leaf-similar-trees
0987-vertical-order-traversal-of-a-binary-tree
1008-construct-binary-search-tree-from-preorder-traversal
2265-count-nodes-equal-to-average-of-subtree
3997-count-dominant-nodes-in-a-binary-tree
4015-weighted-sum-of-a-tree

Breadth-First Search

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
0117-populating-next-right-pointers-in-each-node-ii
0126-word-ladder-ii
0127-word-ladder
0130-surrounded-regions
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0542-01-matrix
0547-number-of-provinces
0662-maximum-width-of-binary-tree
0733-flood-fill
0863-all-nodes-distance-k-in-binary-tree
0987-vertical-order-traversal-of-a-binary-tree
0994-rotting-oranges
1020-number-of-enclaves
1096-brace-expansion-ii
2492-minimum-score-of-a-path-between-two-cities
2812-find-the-safest-path-in-a-grid
3286-find-a-safe-walk-through-a-grid
3310-remove-methods-from-project
3568-minimum-moves-to-clean-the-classroom

Binary Tree

0094-binary-tree-inorder-traversal
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-binary-search-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
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0222-count-complete-tree-nodes
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0450-delete-node-in-a-bst
0662-maximum-width-of-binary-tree
0700-search-in-a-binary-search-tree
0701-insert-into-a-binary-search-tree
0863-all-nodes-distance-k-in-binary-tree
0872-leaf-similar-trees
0987-vertical-order-traversal-of-a-binary-tree
1008-construct-binary-search-tree-from-preorder-traversal
2265-count-nodes-equal-to-average-of-subtree
3997-count-dominant-nodes-in-a-binary-tree

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0006-zigzag-conversion
0008-string-to-integer-atoi
0010-regular-expression-matching
0022-generate-parentheses
0065-valid-number
0087-scramble-string
0091-decode-ways
0115-distinct-subsequences
0126-word-ladder-ii
0127-word-ladder
0132-palindrome-partitioning-ii
0140-word-break-ii
0940-distinct-subsequences-ii
1032-stream-of-characters
1081-smallest-subsequence-of-distinct-characters
1096-brace-expansion-ii
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses
1358-number-of-substrings-containing-all-three-characters
1520-maximum-number-of-non-overlapping-substrings
1807-evaluate-the-bracket-pairs-of-a-string
1927-sum-game
1967-number-of-strings-that-appear-as-substrings-in-word
2213-longest-substring-of-one-repeating-character
2472-maximum-number-of-non-overlapping-palindrome-substrings
2904-shortest-and-lexicographically-smallest-beautiful-string
3014-minimum-number-of-pushes-to-type-word-i
3090-maximum-length-substring-with-two-occurrences
3302-find-the-lexicographically-smallest-valid-sequence
3348-smallest-divisible-digit-product-ii
3498-reverse-degree-of-a-string
3499-maximize-active-section-with-trade-i
3501-maximize-active-section-with-trade-ii
3517-smallest-palindromic-rearrangement-i
3518-smallest-palindromic-rearrangement-ii
3720-lexicographically-smallest-permutation-greater-than-target
3734-lexicographically-smallest-palindromic-permutation-greater-than-target
3756-concatenate-non-zero-digits-and-multiply-by-sum-ii
3992-rearrange-string-to-avoid-character-pair
3998-transform-binary-string-using-subsequence-sort
4021-minimum-operations-to-make-a-rotated-palindrome-i
4026-maximum-gap-between-stations

Array

0001-two-sum
0004-median-of-two-sorted-arrays
0063-unique-paths-ii
0064-minimum-path-sum
0088-merge-sorted-array
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
0119-pascals-triangle-ii
0120-triangle
0121-best-time-to-buy-and-sell-stock
0122-best-time-to-buy-and-sell-stock-ii
0123-best-time-to-buy-and-sell-stock-iii
0130-surrounded-regions
0134-gas-station
0137-single-number-ii
0140-word-break-ii
0149-max-points-on-a-line
0152-maximum-product-subarray
0164-maximum-gap
0200-number-of-islands
0204-count-primes
0381-insert-delete-getrandom-o1-duplicates-allowed
0442-find-all-duplicates-in-an-array
0486-predict-the-winner
0542-01-matrix
0628-maximum-product-of-three-numbers
0645-set-mismatch
0733-flood-fill
0739-daily-temperatures
0835-image-overlap
0994-rotting-oranges
1008-construct-binary-search-tree-from-preorder-traversal
1020-number-of-enclaves
1032-stream-of-characters
1140-stone-game-ii
1260-shift-2d-grid
1288-remove-covered-intervals
1301-number-of-paths-with-max-score
1331-rank-transform-of-an-array
1386-cinema-seat-allocation
1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit
1476-subrectangle-queries
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1807-evaluate-the-bracket-pairs-of-a-string
1846-maximum-element-after-decreasing-and-rearranging
1872-stone-game-viii
1944-number-of-visible-people-in-a-queue
1967-number-of-strings-that-appear-as-substrings-in-word
1979-find-greatest-common-divisor-of-array
2029-stone-game-ix
2043-simple-bank-system
2080-range-frequency-queries
2091-removing-minimum-and-maximum-from-array
2213-longest-substring-of-one-repeating-character
2812-find-the-safest-path-in-a-grid
2948-make-lexicographically-smallest-array-by-swapping-elements
2958-length-of-longest-subarray-with-at-most-k-frequency
3020-find-the-maximum-number-of-elements-in-subset
3069-distribute-elements-into-two-arrays-i
3116-kth-smallest-amount-with-single-denomination-combination
3286-find-a-safe-walk-through-a-grid
3312-sorted-gcd-pair-queries
3336-find-the-number-of-subsequences-with-equal-gcd
3414-maximum-score-of-non-overlapping-intervals
3471-find-the-largest-almost-missing-integer
3483-unique-3-digit-even-numbers
3501-maximize-active-section-with-trade-ii
3513-number-of-unique-xor-triplets-i
3514-number-of-unique-xor-triplets-ii
3524-find-x-value-of-array-i
3525-find-x-value-of-array-ii
3532-path-existence-queries-in-a-graph-i
3534-path-existence-queries-in-a-graph-ii
3550-smallest-index-with-digit-sum-equal-to-index
3568-minimum-moves-to-clean-the-classroom
3620-network-recovery-pathways
3702-longest-subsequence-with-non-zero-bitwise-xor
3718-smallest-missing-multiple-of-k
3731-find-missing-elements
3739-count-subarrays-with-majority-element-ii
3761-minimum-absolute-distance-between-mirror-pairs
3875-construct-uniform-parity-array-i
3876-construct-uniform-parity-array-ii
3903-smallest-stable-index-i
3904-smallest-stable-index-ii
3994-minimum-adjacent-swaps-to-partition-array
3996-even-number-of-knight-moves
3998-transform-binary-string-using-subsequence-sort
4007-widest-possible-fence
4010-maximize-pair-strength-using-gcd
4011-count-subarrays-with-even-odd-ratio-i
4014-minimum-total-price-after-applying-discounts
4015-weighted-sum-of-a-tree
4020-elevator-requests-i
4024-nearest-available-drone
4025-minimize-the-maximum-waiting-time-at-synchronized-traffic-lights

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0106-construct-binary-tree-from-inorder-and-postorder-traversal
0126-word-ladder-ii
0127-word-ladder
0140-word-break-ii
0146-lru-cache
0149-max-points-on-a-line
0352-data-stream-as-disjoint-intervals
0355-design-twitter
0381-insert-delete-getrandom-o1-duplicates-allowed
0432-all-oone-data-structure
0442-find-all-duplicates-in-an-array
0460-lfu-cache
0645-set-mismatch
0863-all-nodes-distance-k-in-binary-tree
0987-vertical-order-traversal-of-a-binary-tree
1015-smallest-integer-divisible-by-k
1096-brace-expansion-ii
1331-rank-transform-of-an-array
1358-number-of-substrings-containing-all-three-characters
1386-cinema-seat-allocation
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
1520-maximum-number-of-non-overlapping-substrings
1807-evaluate-the-bracket-pairs-of-a-string
2043-simple-bank-system
2080-range-frequency-queries
2958-length-of-longest-subarray-with-at-most-k-frequency
3020-find-the-maximum-number-of-elements-in-subset
3090-maximum-length-substring-with-two-occurrences
3312-sorted-gcd-pair-queries
3471-find-the-largest-almost-missing-integer
3483-unique-3-digit-even-numbers
3518-smallest-palindromic-rearrangement-ii
3532-path-existence-queries-in-a-graph-i
3568-minimum-moves-to-clean-the-classroom
3718-smallest-missing-multiple-of-k
3720-lexicographically-smallest-permutation-greater-than-target
3731-find-missing-elements
3739-count-subarrays-with-majority-element-ii
3761-minimum-absolute-distance-between-mirror-pairs
4007-widest-possible-fence

Divide and Conquer

0004-median-of-two-sorted-arrays
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
3739-count-subarrays-with-majority-element-ii
4011-count-subarrays-with-even-odd-ratio-i

Segment Tree

2080-range-frequency-queries
2213-longest-substring-of-one-repeating-character
3501-maximize-active-section-with-trade-ii
3525-find-x-value-of-array-ii
3739-count-subarrays-with-majority-element-ii
4011-count-subarrays-with-even-odd-ratio-i

Merge Sort

3739-count-subarrays-with-majority-element-ii
4011-count-subarrays-with-even-odd-ratio-i

Prefix Sum

1140-stone-game-ii
1621-number-of-sets-of-k-non-overlapping-line-segments
1872-stone-game-viii
3312-sorted-gcd-pair-queries
3739-count-subarrays-with-majority-element-ii
3756-concatenate-non-zero-digits-and-multiply-by-sum-ii
3903-smallest-stable-index-i
3904-smallest-stable-index-ii
4011-count-subarrays-with-even-odd-ratio-i

Enumeration

0204-count-primes
1291-sequential-digits
3020-find-the-maximum-number-of-elements-in-subset
3345-smallest-divisible-digit-product-i
3483-unique-3-digit-even-numbers
3499-maximize-active-section-with-trade-i
3514-number-of-unique-xor-triplets-ii
3720-lexicographically-smallest-permutation-greater-than-target
3734-lexicographically-smallest-palindromic-permutation-greater-than-target
4007-widest-possible-fence
4010-maximize-pair-strength-using-gcd
4021-minimum-operations-to-make-a-rotated-palindrome-i
4024-nearest-available-drone

Linked List

0002-add-two-numbers
0086-partition-list
0092-reverse-linked-list-ii
0109-convert-sorted-list-to-binary-search-tree
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0143-reorder-list
0146-lru-cache
0355-design-twitter
0432-all-oone-data-structure
0460-lfu-cache
2058-find-the-minimum-and-maximum-number-of-nodes-between-critical-points

Two Pointers

0005-longest-palindromic-substring
0086-partition-list
0088-merge-sorted-array
0143-reorder-list
2472-maximum-number-of-non-overlapping-palindrome-substrings
3302-find-the-lexicographically-smallest-valid-sequence
3534-path-existence-queries-in-a-graph-ii
3734-lexicographically-smallest-palindromic-permutation-greater-than-target
3992-rearrange-string-to-avoid-character-pair
3998-transform-binary-string-using-subsequence-sort
4014-minimum-total-price-after-applying-discounts
4026-maximum-gap-between-stations

Dynamic Programming

0005-longest-palindromic-substring
0010-regular-expression-matching
0022-generate-parentheses
0063-unique-paths-ii
0064-minimum-path-sum
0087-scramble-string
0091-decode-ways
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0115-distinct-subsequences
0119-pascals-triangle-ii
0120-triangle
0121-best-time-to-buy-and-sell-stock
0122-best-time-to-buy-and-sell-stock-ii
0123-best-time-to-buy-and-sell-stock-iii
0124-binary-tree-maximum-path-sum
0132-palindrome-partitioning-ii
0140-word-break-ii
0152-maximum-product-subarray
0486-predict-the-winner
0542-01-matrix
0940-distinct-subsequences-ii
1140-stone-game-ii
1301-number-of-paths-with-max-score
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
1872-stone-game-viii
2472-maximum-number-of-non-overlapping-palindrome-substrings
3302-find-the-lexicographically-smallest-valid-sequence
3336-find-the-number-of-subsequences-with-equal-gcd
3414-maximum-score-of-non-overlapping-intervals
3524-find-x-value-of-array-i
3534-path-existence-queries-in-a-graph-ii
3620-network-recovery-pathways

Sorting

0088-merge-sorted-array
0164-maximum-gap
0442-find-all-duplicates-in-an-array
0628-maximum-product-of-three-numbers
0645-set-mismatch
0987-vertical-order-traversal-of-a-binary-tree
1096-brace-expansion-ii
1288-remove-covered-intervals
1331-rank-transform-of-an-array
1520-maximum-number-of-non-overlapping-substrings
1846-maximum-element-after-decreasing-and-rearranging
2948-make-lexicographically-smallest-array-by-swapping-elements
3414-maximum-score-of-non-overlapping-intervals
3517-smallest-palindromic-rearrangement-i
3534-path-existence-queries-in-a-graph-ii
3536-maximum-product-of-two-digits
3731-find-missing-elements
3992-rearrange-string-to-avoid-character-pair
4014-minimum-total-price-after-applying-discounts

Math

0002-add-two-numbers
0007-reverse-integer
0009-palindrome-number
0089-gray-code
0096-unique-binary-search-trees
0149-max-points-on-a-line
0204-count-primes
0263-ugly-number
0381-insert-delete-getrandom-o1-duplicates-allowed
0486-predict-the-winner
0628-maximum-product-of-three-numbers
0728-self-dividing-numbers
0836-rectangle-overlap
1015-smallest-integer-divisible-by-k
1140-stone-game-ii
1401-circle-and-rectangle-overlapping
1510-stone-game-iv
1621-number-of-sets-of-k-non-overlapping-line-segments
1872-stone-game-viii
1927-sum-game
1979-find-greatest-common-divisor-of-array
2029-stone-game-ix
3014-minimum-number-of-pushes-to-type-word-i
3116-kth-smallest-amount-with-single-denomination-combination
3312-sorted-gcd-pair-queries
3336-find-the-number-of-subsequences-with-equal-gcd
3345-smallest-divisible-digit-product-i
3348-smallest-divisible-digit-product-ii
3513-number-of-unique-xor-triplets-i
3514-number-of-unique-xor-triplets-ii
3518-smallest-palindromic-rearrangement-ii
3524-find-x-value-of-array-i
3525-find-x-value-of-array-ii
3536-maximum-product-of-two-digits
3550-smallest-index-with-digit-sum-equal-to-index
3622-check-divisibility-by-digit-sum-and-product
3658-gcd-of-odd-and-even-sums
3754-concatenate-non-zero-digits-and-multiply-by-sum-i
3756-concatenate-non-zero-digits-and-multiply-by-sum-ii
3761-minimum-absolute-distance-between-mirror-pairs
3783-mirror-distance-of-an-integer
3870-count-commas-in-range
3871-count-commas-in-range-ii
3875-construct-uniform-parity-array-i
3876-construct-uniform-parity-array-ii
3993-maximum-value-of-an-alternating-sequence
3996-even-number-of-knight-moves
4010-maximize-pair-strength-using-gcd
4021-minimum-operations-to-make-a-rotated-palindrome-i

Backtracking

0022-generate-parentheses
0089-gray-code
0095-unique-binary-search-trees-ii
0113-path-sum-ii
0126-word-ladder-ii
0140-word-break-ii
1096-brace-expansion-ii
3348-smallest-divisible-digit-product-ii

Bit Manipulation

0089-gray-code
0137-single-number-ii
0201-bitwise-and-of-numbers-range
0222-count-complete-tree-nodes
0645-set-mismatch
1386-cinema-seat-allocation
3116-kth-smallest-amount-with-single-denomination-combination
3513-number-of-unique-xor-triplets-i
3514-number-of-unique-xor-triplets-ii
3534-path-existence-queries-in-a-graph-ii
3568-minimum-moves-to-clean-the-classroom
3702-longest-subsequence-with-non-zero-bitwise-xor

Greedy

0122-best-time-to-buy-and-sell-stock-ii
0134-gas-station
1081-smallest-subsequence-of-distinct-characters
1386-cinema-seat-allocation
1520-maximum-number-of-non-overlapping-substrings
1846-maximum-element-after-decreasing-and-rearranging
1927-sum-game
2029-stone-game-ix
2091-removing-minimum-and-maximum-from-array
2472-maximum-number-of-non-overlapping-palindrome-substrings
3014-minimum-number-of-pushes-to-type-word-i
3302-find-the-lexicographically-smallest-valid-sequence
3348-smallest-divisible-digit-product-ii
3534-path-existence-queries-in-a-graph-ii
3720-lexicographically-smallest-permutation-greater-than-target
3993-maximum-value-of-an-alternating-sequence
3994-minimum-adjacent-swaps-to-partition-array
3998-transform-binary-string-using-subsequence-sort
4014-minimum-total-price-after-applying-discounts
4025-minimize-the-maximum-waiting-time-at-synchronized-traffic-lights
4026-maximum-gap-between-stations

Design

0146-lru-cache
0352-data-stream-as-disjoint-intervals
0355-design-twitter
0381-insert-delete-getrandom-o1-duplicates-allowed
0432-all-oone-data-structure
0460-lfu-cache
1032-stream-of-characters
1476-subrectangle-queries
2043-simple-bank-system
2080-range-frequency-queries

Doubly-Linked List

0146-lru-cache
0432-all-oone-data-structure
0460-lfu-cache

Sliding Window

0003-longest-substring-without-repeating-characters
1358-number-of-substrings-containing-all-three-characters
1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
2904-shortest-and-lexicographically-smallest-beautiful-string
2958-length-of-longest-subarray-with-at-most-k-frequency
3090-maximum-length-substring-with-two-occurrences

Trie

0140-word-break-ii
1032-stream-of-characters

Data Stream

0352-data-stream-as-disjoint-intervals
1032-stream-of-characters

Binary Search

0004-median-of-two-sorted-arrays
0222-count-complete-tree-nodes
0352-data-stream-as-disjoint-intervals
1477-find-two-non-overlapping-sub-arrays-each-with-target-sum
2080-range-frequency-queries
2812-find-the-safest-path-in-a-grid
3116-kth-smallest-amount-with-single-denomination-combination
3312-sorted-gcd-pair-queries
3414-maximum-score-of-non-overlapping-intervals
3501-maximize-active-section-with-trade-ii
3532-path-existence-queries-in-a-graph-i
3534-path-existence-queries-in-a-graph-ii
3620-network-recovery-pathways

Union-Find

0130-surrounded-regions
0200-number-of-islands
0352-data-stream-as-disjoint-intervals
0547-number-of-provinces
1020-number-of-enclaves
2492-minimum-score-of-a-path-between-two-cities
2812-find-the-safest-path-in-a-grid
2948-make-lexicographically-smallest-array-by-swapping-elements
3532-path-existence-queries-in-a-graph-i

Ordered Set

0352-data-stream-as-disjoint-intervals
1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit
2213-longest-substring-of-one-repeating-character

Randomized

0381-insert-delete-getrandom-o1-duplicates-allowed

Matrix

0063-unique-paths-ii
0064-minimum-path-sum
0130-surrounded-regions
0200-number-of-islands
0542-01-matrix
0733-flood-fill
0835-image-overlap
0994-rotting-oranges
1020-number-of-enclaves
1260-shift-2d-grid
1301-number-of-paths-with-max-score
1476-subrectangle-queries
2812-find-the-safest-path-in-a-grid
3286-find-a-safe-walk-through-a-grid
3568-minimum-moves-to-clean-the-classroom

Heap (Priority Queue)

0355-design-twitter
1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit
2812-find-the-safest-path-in-a-grid
3286-find-a-safe-walk-through-a-grid
3620-network-recovery-pathways

Simulation

1260-shift-2d-grid
2043-simple-bank-system
3069-distribute-elements-into-two-arrays-i
3498-reverse-degree-of-a-string
4020-elevator-requests-i

Binary Search Tree

0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0098-validate-binary-search-tree
0099-recover-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
0450-delete-node-in-a-bst
0700-search-in-a-binary-search-tree
0701-insert-into-a-binary-search-tree
1008-construct-binary-search-tree-from-preorder-traversal

Graph Theory

0207-course-schedule
0547-number-of-provinces
2492-minimum-score-of-a-path-between-two-cities
3286-find-a-safe-walk-through-a-grid
3310-remove-methods-from-project
3532-path-existence-queries-in-a-graph-i
3534-path-existence-queries-in-a-graph-ii
3620-network-recovery-pathways

Shortest Path

3286-find-a-safe-walk-through-a-grid
3620-network-recovery-pathways

Topological Sort

0207-course-schedule
3620-network-recovery-pathways

Depth-First Search

0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0099-recover-binary-search-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
0114-flatten-binary-tree-to-linked-list
0116-populating-next-right-pointers-in-each-node
0117-populating-next-right-pointers-in-each-node-ii
0124-binary-tree-maximum-path-sum
0129-sum-root-to-leaf-numbers
0130-surrounded-regions
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0199-binary-tree-right-side-view
0200-number-of-islands
0207-course-schedule
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0547-number-of-provinces
0662-maximum-width-of-binary-tree
0733-flood-fill
0863-all-nodes-distance-k-in-binary-tree
0872-leaf-similar-trees
0987-vertical-order-traversal-of-a-binary-tree
1020-number-of-enclaves
2265-count-nodes-equal-to-average-of-subtree
2492-minimum-score-of-a-path-between-two-cities
3310-remove-methods-from-project
3997-count-dominant-nodes-in-a-binary-tree
4015-weighted-sum-of-a-tree

Recursion

0002-add-two-numbers
0010-regular-expression-matching
0143-reorder-list
0486-predict-the-winner
3483-unique-3-digit-even-numbers

Number Theory

0204-count-primes
1979-find-greatest-common-divisor-of-array
3116-kth-smallest-amount-with-single-denomination-combination
3312-sorted-gcd-pair-queries
3336-find-the-number-of-subsequences-with-equal-gcd
3348-smallest-divisible-digit-product-ii
3658-gcd-of-odd-and-even-sums
4010-maximize-pair-strength-using-gcd

Geometry

0149-max-points-on-a-line
0836-rectangle-overlap
1401-circle-and-rectangle-overlapping

Combinatorics

1621-number-of-sets-of-k-non-overlapping-line-segments
3116-kth-smallest-amount-with-single-denomination-combination
3312-sorted-gcd-pair-queries
3518-smallest-palindromic-rearrangement-ii

Counting

2029-stone-game-ix
3312-sorted-gcd-pair-queries
3518-smallest-palindromic-rearrangement-ii
3720-lexicographically-smallest-permutation-greater-than-target
4007-widest-possible-fence

Stack

0094-binary-tree-inorder-traversal
0114-flatten-binary-tree-to-linked-list
0143-reorder-list
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0739-daily-temperatures
1008-construct-binary-search-tree-from-preorder-traversal
1081-smallest-subsequence-of-distinct-characters
1096-brace-expansion-ii
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses
1944-number-of-visible-people-in-a-queue

Monotonic Stack

0739-daily-temperatures
1008-construct-binary-search-tree-from-preorder-traversal
1081-smallest-subsequence-of-distinct-characters
1944-number-of-visible-people-in-a-queue

Counting Sort

3517-smallest-palindromic-rearrangement-i

Game Theory

0486-predict-the-winner
1140-stone-game-ii
1510-stone-game-iv
1872-stone-game-viii
1927-sum-game
2029-stone-game-ix

Minimax

1140-stone-game-ii
1510-stone-game-iv
1872-stone-game-viii
2029-stone-game-ix

Zero-Sum Game

1140-stone-game-ii
1510-stone-game-iv
1872-stone-game-viii
2029-stone-game-ix

Nim Game

1510-stone-game-iv
2029-stone-game-ix

Sprague–Grundy Theorem

1510-stone-game-iv

Binary Indexed Tree

4011-count-subarrays-with-even-odd-ratio-i

Bidirectional Search

0126-word-ladder-ii
0127-word-ladder

DP on Trees

0124-binary-tree-maximum-path-sum

Binary Lifting

0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree

Lowest Common Ancestor

0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree

Primality Test

0204-count-primes

Sieve Theory

0204-count-primes

Prime Number Sieve

0204-count-primes

Bracket Sequences

0022-generate-parentheses
1111-maximum-nesting-depth-of-two-valid-parentheses-strings
1190-reverse-substrings-between-each-pair-of-parentheses

Directed Acyclic Graph

0207-course-schedule

Memoization

0140-word-break-ii

Bucket Sort

0164-maximum-gap

Radix Sort

0164-maximum-gap

Pigeonhole Principle

0164-maximum-gap

Database

0182-duplicate-emails
0196-delete-duplicate-emails
0197-rising-temperature

Queue

1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit

Monotonic Queue

1438-longest-continuous-subarray-with-absolute-diff-less-than-or-equal-to-limit