alg-leet-code

Collection of LeetCode questions to ace the coding interview! - Created using LeetHub

LeetCode Topics

Array

0001-two-sum
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
0039-combination-sum
0049-group-anagrams
0053-maximum-subarray
0054-spiral-matrix
0056-merge-intervals
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0079-word-search
0088-merge-sorted-array
0118-pascals-triangle
0119-pascals-triangle-ii
0121-best-time-to-buy-and-sell-stock
0128-longest-consecutive-sequence
0134-gas-station
0136-single-number
0139-word-break
0152-maximum-product-subarray
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0169-majority-element
0198-house-robber
0200-number-of-islands
0209-minimum-size-subarray-sum
0213-house-robber-ii
0215-kth-largest-element-in-an-array
0219-contains-duplicate-ii
0238-product-of-array-except-self
0268-missing-number
0275-h-index-ii
0283-move-zeroes
0300-longest-increasing-subsequence
0303-range-sum-query-immutable
0322-coin-change
0334-increasing-triplet-subsequence
0347-top-k-frequent-elements
0350-intersection-of-two-arrays-ii
0417-pacific-atlantic-water-flow
0435-non-overlapping-intervals
0436-find-right-interval
0452-minimum-number-of-arrows-to-burst-balloons
0455-assign-cookies
0525-contiguous-array
0540-single-element-in-a-sorted-array
0561-array-partition
0594-longest-harmonious-subsequence
0605-can-place-flowers
0611-valid-triangle-number
0643-maximum-average-subarray-i
0646-maximum-length-of-pair-chain
0661-image-smoother
0695-max-area-of-island
0714-best-time-to-buy-and-sell-stock-with-transaction-fee
0724-find-pivot-index
0733-flood-fill
0735-asteroid-collision
0739-daily-temperatures
0745-find-smallest-letter-greater-than-target
0747-min-cost-climbing-stairs
0792-binary-search
0797-rabbits-in-forest
0861-flipping-an-image
0882-peak-index-in-a-mountain-array
0890-lemonade-change
0898-transpose-matrix
0907-koko-eating-bananas
0979-di-string-match
1009-pancake-sorting
1018-largest-perimeter-triangle
1019-squares-of-a-sorted-array
1036-rotting-oranges
1046-max-consecutive-ones-iii
1095-two-city-scheduling
1217-relative-sort-array
1249-snapshot-array
1319-unique-number-of-occurrences
1329-minimum-cost-to-move-chips-to-the-same-position
1378-cells-with-odd-values-in-a-matrix
1392-find-the-difference-of-two-arrays
1397-search-suggestions-system
1476-count-negative-numbers-in-a-sorted-matrix
1519-minimum-subsequence-in-non-increasing-order
1528-kids-with-the-greatest-number-of-candies
1582-design-browser-history
1586-longest-subarray-of-1s-after-deleting-one-element
1603-running-sum-of-1d-array
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1646-kth-missing-positive-number
1781-check-if-two-string-arrays-are-equivalent
1786-count-the-number-of-consistent-strings
1791-richest-customer-wealth
1798-max-number-of-k-sum-pairs
1829-maximum-units-on-a-truck
1833-find-the-highest-altitude
1938-minimum-operations-to-make-the-array-increasing
2038-nearest-exit-from-entrance-in-maze
2077-largest-number-after-mutating-substring
2148-minimum-number-of-moves-to-seat-everyone
2188-minimized-maximum-of-products-distributed-to-any-store
2199-two-furthest-houses-with-different-colors
2219-maximum-number-of-words-found-in-sentences
2231-find-first-palindromic-string-in-the-array
2248-minimum-cost-of-buying-candies-with-discount
2392-successful-pairs-of-spells-and-potions
2412-minimum-amount-of-time-to-fill-cups
2428-equal-row-and-column-pairs
2436-make-array-zero-by-subtracting-equal-amounts
2459-minimum-hours-of-training-to-win-a-competition
2469-longest-subsequence-with-limited-sum
2536-determine-if-two-events-have-conflict
2553-total-cost-to-hire-k-workers
2624-difference-between-element-sum-and-digit-sum-of-an-array
2636-maximum-subsequence-score
2714-left-and-right-sum-differences
2756-buy-two-chocolates
2767-maximum-sum-with-exactly-k-elements
2844-sum-of-squares-of-special-elements
2876-number-of-employees-who-met-the-target
3143-longest-unequal-adjacent-groups-subsequence-i
3194-find-words-containing-character
3206-find-common-elements-between-two-arrays
3221-find-the-peaks
3226-minimum-number-game
3227-find-missing-and-repeated-values
3321-type-of-triangle
3779-eat-pizzas
3788-maximum-unique-subarray-sum-after-deletion

Prefix Sum

0209-minimum-size-subarray-sum
0238-product-of-array-except-self
0303-range-sum-query-immutable
0525-contiguous-array
0724-find-pivot-index
1046-max-consecutive-ones-iii
1603-running-sum-of-1d-array
1833-find-the-highest-altitude
2469-longest-subsequence-with-limited-sum
2714-left-and-right-sum-differences

Matrix

0054-spiral-matrix
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0079-word-search
0200-number-of-islands
0417-pacific-atlantic-water-flow
0661-image-smoother
0695-max-area-of-island
0733-flood-fill
0861-flipping-an-image
0898-transpose-matrix
1036-rotting-oranges
1476-count-negative-numbers-in-a-sorted-matrix
1791-richest-customer-wealth
2038-nearest-exit-from-entrance-in-maze
2428-equal-row-and-column-pairs
3227-find-missing-and-repeated-values

Math

0062-unique-paths
0069-sqrtx
0070-climbing-stairs
0258-add-digits
0268-missing-number
0367-valid-perfect-square
0371-sum-of-two-integers
0412-fizz-buzz
0441-arranging-coins
0797-rabbits-in-forest
1013-fibonacci-number
1018-largest-perimeter-triangle
1086-divisor-game
1146-greatest-common-divisor-of-strings
1236-n-th-tribonacci-number
1329-minimum-cost-to-move-chips-to-the-same-position
1378-cells-with-odd-values-in-a-matrix
1406-subtract-the-product-and-sum-of-digits-of-an-integer
1444-number-of-steps-to-reduce-a-number-to-zero
1448-maximum-69-number
1610-xor-operation-in-an-array
1861-building-boxes
2032-largest-odd-number-in-string
2264-minimum-sum-of-four-digit-number-after-splitting-digits
2608-count-the-digits-that-divide-a-number
2624-difference-between-element-sum-and-digit-sum-of-an-array
2663-distribute-money-to-maximum-children
2704-maximum-difference-by-remapping-a-digit
2715-k-items-with-the-maximum-sum
2752-sum-multiples
2812-find-the-maximum-achievable-number
3055-maximum-odd-binary-number
3172-divisible-and-non-divisible-sums-difference
3227-find-missing-and-repeated-values
3275-minimum-number-of-pushes-to-type-word-i
3321-type-of-triangle
3625-stone-removal-game

String

0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0014-longest-common-prefix
0017-letter-combinations-of-a-phone-number
0020-valid-parentheses
0028-find-the-index-of-the-first-occurrence-in-a-string
0049-group-anagrams
0072-edit-distance
0079-word-search
0125-valid-palindrome
0139-word-break
0151-reverse-words-in-a-string
0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure
0242-valid-anagram
0344-reverse-string
0345-reverse-vowels-of-a-string
0383-ransom-note
0387-first-unique-character-in-a-string
0392-is-subsequence
0394-decode-string
0409-longest-palindrome
0412-fizz-buzz
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0443-string-compression
0520-detect-capital
0583-delete-operation-for-two-strings
0647-palindromic-substrings
0649-dota2-senate
0680-valid-palindrome-ii
0742-to-lower-case
0778-reorganize-string
0979-di-string-match
1023-time-based-key-value-store
1146-greatest-common-divisor-of-strings
1250-longest-common-subsequence
1304-longest-happy-string
1341-split-a-string-in-balanced-strings
1397-search-suggestions-system
1567-maximum-number-of-vowels-in-a-substring-of-given-length
1764-maximum-repeating-substring
1777-determine-if-two-strings-are-close
1781-check-if-two-string-arrays-are-equivalent
1786-count-the-number-of-consistent-strings
1858-latest-time-by-replacing-hidden-digits
1894-merge-strings-alternately
1960-check-if-the-sentence-is-pangram
1987-substrings-of-size-three-with-distinct-characters
2011-maximum-value-after-insertion
2032-largest-odd-number-in-string
2077-largest-number-after-mutating-substring
2088-minimum-time-to-type-word-using-special-typewriter
2219-maximum-number-of-words-found-in-sentences
2231-find-first-palindromic-string-in-the-array
2235-capitalize-the-title
2337-remove-digit-from-number-to-maximize-result
2345-minimum-number-of-operations-to-convert-time
2536-determine-if-two-events-have-conflict
2816-lexicographically-smallest-palindrome
3055-maximum-odd-binary-number
3143-longest-unequal-adjacent-groups-subsequence-i
3194-find-words-containing-character
3207-make-three-strings-equal
3275-minimum-number-of-pushes-to-type-word-i
3312-number-of-changing-keys

Simulation

0054-spiral-matrix
0258-add-digits
0412-fizz-buzz
0735-asteroid-collision
0861-flipping-an-image
0898-transpose-matrix
1378-cells-with-odd-values-in-a-matrix
2428-equal-row-and-column-pairs
2436-make-array-zero-by-subtracting-equal-amounts
2553-total-cost-to-hire-k-workers
3226-minimum-number-game
3625-stone-removal-game

Bit Manipulation

0136-single-number
0191-number-of-1-bits
0268-missing-number
0338-counting-bits
0371-sum-of-two-integers
0861-flipping-an-image
1441-minimum-flips-to-make-a-or-b-equal-to-c
1444-number-of-steps-to-reduce-a-number-to-zero
1610-xor-operation-in-an-array
1786-count-the-number-of-consistent-strings

Linked List

0021-merge-two-sorted-lists
0141-linked-list-cycle
0143-reorder-list
0206-reverse-linked-list
0328-odd-even-linked-list
0908-middle-of-the-linked-list
1582-design-browser-history
2216-delete-the-middle-node-of-a-linked-list
2236-maximum-twin-sum-of-a-linked-list

Two Pointers

0005-longest-palindromic-substring
0011-container-with-most-water
0015-3sum
0026-remove-duplicates-from-sorted-array
0027-remove-element
0028-find-the-index-of-the-first-occurrence-in-a-string
0088-merge-sorted-array
0125-valid-palindrome
0141-linked-list-cycle
0143-reorder-list
0151-reverse-words-in-a-string
0167-two-sum-ii-input-array-is-sorted
0283-move-zeroes
0344-reverse-string
0345-reverse-vowels-of-a-string
0350-intersection-of-two-arrays-ii
0392-is-subsequence
0443-string-compression
0455-assign-cookies
0611-valid-triangle-number
0647-palindromic-substrings
0680-valid-palindrome-ii
0861-flipping-an-image
0908-middle-of-the-linked-list
0979-di-string-match
1009-pancake-sorting
1019-squares-of-a-sorted-array
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1798-max-number-of-k-sum-pairs
1894-merge-strings-alternately
2216-delete-the-middle-node-of-a-linked-list
2231-find-first-palindromic-string-in-the-array
2236-maximum-twin-sum-of-a-linked-list
2392-successful-pairs-of-spells-and-potions
2553-total-cost-to-hire-k-workers
2816-lexicographically-smallest-palindrome

Hash Table

0001-two-sum
0003-longest-substring-without-repeating-characters
0017-letter-combinations-of-a-phone-number
0049-group-anagrams
0073-set-matrix-zeroes
0128-longest-consecutive-sequence
0133-clone-graph
0139-word-break
0141-linked-list-cycle
0169-majority-element
0208-implement-trie-prefix-tree
0219-contains-duplicate-ii
0242-valid-anagram
0268-missing-number
0347-top-k-frequent-elements
0350-intersection-of-two-arrays-ii
0383-ransom-note
0387-first-unique-character-in-a-string
0409-longest-palindrome
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0525-contiguous-array
0594-longest-harmonious-subsequence
0778-reorganize-string
0797-rabbits-in-forest
1023-time-based-key-value-store
1217-relative-sort-array
1249-snapshot-array
1319-unique-number-of-occurrences
1392-find-the-difference-of-two-arrays
1777-determine-if-two-strings-are-close
1786-count-the-number-of-consistent-strings
1798-max-number-of-k-sum-pairs
1960-check-if-the-sentence-is-pangram
1987-substrings-of-size-three-with-distinct-characters
2413-smallest-number-in-infinite-set
2428-equal-row-and-column-pairs
2436-make-array-zero-by-subtracting-equal-amounts
3206-find-common-elements-between-two-arrays
3227-find-missing-and-repeated-values
3788-maximum-unique-subarray-sum-after-deletion

Counting

0169-majority-element
0347-top-k-frequent-elements
0383-ransom-note
0387-first-unique-character-in-a-string
0594-longest-harmonious-subsequence
0778-reorganize-string
1341-split-a-string-in-balanced-strings
1777-determine-if-two-strings-are-close
1786-count-the-number-of-consistent-strings
1987-substrings-of-size-three-with-distinct-characters

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
0074-search-a-2d-matrix
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0209-minimum-size-subarray-sum
0268-missing-number
0275-h-index-ii
0278-first-bad-version
0300-longest-increasing-subsequence
0350-intersection-of-two-arrays-ii
0367-valid-perfect-square
0374-guess-number-higher-or-lower
0436-find-right-interval
0441-arranging-coins
0540-single-element-in-a-sorted-array
0611-valid-triangle-number
0745-find-smallest-letter-greater-than-target
0792-binary-search
0882-peak-index-in-a-mountain-array
0907-koko-eating-bananas
1023-time-based-key-value-store
1046-max-consecutive-ones-iii
1249-snapshot-array
1397-search-suggestions-system
1476-count-negative-numbers-in-a-sorted-matrix
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1646-kth-missing-positive-number
1861-building-boxes
2188-minimized-maximum-of-products-distributed-to-any-store
2392-successful-pairs-of-spells-and-potions
2469-longest-subsequence-with-limited-sum

Interactive

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

Sorting

0015-3sum
0049-group-anagrams
0056-merge-intervals
0088-merge-sorted-array
0169-majority-element
0215-kth-largest-element-in-an-array
0242-valid-anagram
0268-missing-number
0347-top-k-frequent-elements
0350-intersection-of-two-arrays-ii
0435-non-overlapping-intervals
0436-find-right-interval
0452-minimum-number-of-arrows-to-burst-balloons
0455-assign-cookies
0561-array-partition
0594-longest-harmonious-subsequence
0611-valid-triangle-number
0646-maximum-length-of-pair-chain
0778-reorganize-string
1009-pancake-sorting
1018-largest-perimeter-triangle
1019-squares-of-a-sorted-array
1095-two-city-scheduling
1217-relative-sort-array
1397-search-suggestions-system
1519-minimum-subsequence-in-non-increasing-order
1621-number-of-subsequences-that-satisfy-the-given-sum-condition
1777-determine-if-two-strings-are-close
1798-max-number-of-k-sum-pairs
1829-maximum-units-on-a-truck
2148-minimum-number-of-moves-to-seat-everyone
2248-minimum-cost-of-buying-candies-with-discount
2264-minimum-sum-of-four-digit-number-after-splitting-digits
2392-successful-pairs-of-spells-and-potions
2412-minimum-amount-of-time-to-fill-cups
2436-make-array-zero-by-subtracting-equal-amounts
2469-longest-subsequence-with-limited-sum
2636-maximum-subsequence-score
2756-buy-two-chocolates
3226-minimum-number-game
3321-type-of-triangle
3779-eat-pizzas

Design

0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure
0232-implement-queue-using-stacks
0303-range-sum-query-immutable
0937-online-stock-span
0969-number-of-recent-calls
1023-time-based-key-value-store
1249-snapshot-array
1582-design-browser-history
2413-smallest-number-in-infinite-set

Greedy

0011-container-with-most-water
0134-gas-station
0334-increasing-triplet-subsequence
0409-longest-palindrome
0435-non-overlapping-intervals
0452-minimum-number-of-arrows-to-burst-balloons
0455-assign-cookies
0561-array-partition
0605-can-place-flowers
0611-valid-triangle-number
0646-maximum-length-of-pair-chain
0649-dota2-senate
0680-valid-palindrome-ii
0714-best-time-to-buy-and-sell-stock-with-transaction-fee
0778-reorganize-string
0797-rabbits-in-forest
0890-lemonade-change
0979-di-string-match
1009-pancake-sorting
1018-largest-perimeter-triangle
1095-two-city-scheduling
1304-longest-happy-string
1329-minimum-cost-to-move-chips-to-the-same-position
1341-split-a-string-in-balanced-strings
1448-maximum-69-number
1519-minimum-subsequence-in-non-increasing-order
1829-maximum-units-on-a-truck
1858-latest-time-by-replacing-hidden-digits
1861-building-boxes
1938-minimum-operations-to-make-the-array-increasing
2011-maximum-value-after-insertion
2032-largest-odd-number-in-string
2077-largest-number-after-mutating-substring
2088-minimum-time-to-type-word-using-special-typewriter
2148-minimum-number-of-moves-to-seat-everyone
2188-minimized-maximum-of-products-distributed-to-any-store
2199-two-furthest-houses-with-different-colors
2248-minimum-cost-of-buying-candies-with-discount
2264-minimum-sum-of-four-digit-number-after-splitting-digits
2337-remove-digit-from-number-to-maximize-result
2345-minimum-number-of-operations-to-convert-time
2412-minimum-amount-of-time-to-fill-cups
2436-make-array-zero-by-subtracting-equal-amounts
2459-minimum-hours-of-training-to-win-a-competition
2469-longest-subsequence-with-limited-sum
2636-maximum-subsequence-score
2663-distribute-money-to-maximum-children
2704-maximum-difference-by-remapping-a-digit
2715-k-items-with-the-maximum-sum
2756-buy-two-chocolates
2767-maximum-sum-with-exactly-k-elements
2816-lexicographically-smallest-palindrome
3055-maximum-odd-binary-number
3143-longest-unequal-adjacent-groups-subsequence-i
3275-minimum-number-of-pushes-to-type-word-i
3779-eat-pizzas
3788-maximum-unique-subarray-sum-after-deletion

Queue

0232-implement-queue-using-stacks
0387-first-unique-character-in-a-string
0649-dota2-senate
0969-number-of-recent-calls

String Matching

0028-find-the-index-of-the-first-occurrence-in-a-string
0572-subtree-of-another-tree
1764-maximum-repeating-substring

Trie

0014-longest-common-prefix
0139-word-break
0208-implement-trie-prefix-tree
0211-design-add-and-search-words-data-structure
1397-search-suggestions-system

Dynamic Programming

0005-longest-palindromic-substring
0053-maximum-subarray
0062-unique-paths
0070-climbing-stairs
0072-edit-distance
0118-pascals-triangle
0119-pascals-triangle-ii
0121-best-time-to-buy-and-sell-stock
0139-word-break
0152-maximum-product-subarray
0198-house-robber
0213-house-robber-ii
0300-longest-increasing-subsequence
0322-coin-change
0338-counting-bits
0392-is-subsequence
0435-non-overlapping-intervals
0583-delete-operation-for-two-strings
0646-maximum-length-of-pair-chain
0647-palindromic-substrings
0714-best-time-to-buy-and-sell-stock-with-transaction-fee
0747-min-cost-climbing-stairs
0806-domino-and-tromino-tiling
1013-fibonacci-number
1086-divisor-game
1236-n-th-tribonacci-number
1250-longest-common-subsequence
1586-longest-subarray-of-1s-after-deleting-one-element
1764-maximum-repeating-substring
3143-longest-unequal-adjacent-groups-subsequence-i

Memoization

0070-climbing-stairs
0139-word-break
1013-fibonacci-number
1236-n-th-tribonacci-number

Sliding Window

0003-longest-substring-without-repeating-characters
0209-minimum-size-subarray-sum
0219-contains-duplicate-ii
0424-longest-repeating-character-replacement
0438-find-all-anagrams-in-a-string
0594-longest-harmonious-subsequence
0643-maximum-average-subarray-i
1046-max-consecutive-ones-iii
1567-maximum-number-of-vowels-in-a-substring-of-given-length
1586-longest-subarray-of-1s-after-deleting-one-element
1987-substrings-of-size-three-with-distinct-characters

Data Stream

0937-online-stock-span
0969-number-of-recent-calls
1582-design-browser-history

Recursion

0021-merge-two-sorted-lists
0143-reorder-list
0206-reverse-linked-list
0394-decode-string
1013-fibonacci-number

Stack

0020-valid-parentheses
0143-reorder-list
0144-binary-tree-preorder-traversal
0232-implement-queue-using-stacks
0394-decode-string
0735-asteroid-collision
0739-daily-temperatures
0937-online-stock-span
1582-design-browser-history
2236-maximum-twin-sum-of-a-linked-list

Monotonic Stack

0739-daily-temperatures
0937-online-stock-span

Heap (Priority Queue)

0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
0778-reorganize-string
1304-longest-happy-string
1397-search-suggestions-system
2412-minimum-amount-of-time-to-fill-cups
2413-smallest-number-in-infinite-set
2436-make-array-zero-by-subtracting-equal-amounts
2553-total-cost-to-hire-k-workers
2636-maximum-subsequence-score
3226-minimum-number-game

Combinatorics

0062-unique-paths

Divide and Conquer

0053-maximum-subarray
0169-majority-element
0191-number-of-1-bits
0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements

Quickselect

0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements

Ordered Set

2413-smallest-number-in-infinite-set

Tree

0098-validate-binary-search-tree
0100-same-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0144-binary-tree-preorder-traversal
0450-delete-node-in-a-bst
0572-subtree-of-another-tree
0783-search-in-a-binary-search-tree
0904-leaf-similar-trees

Depth-First Search

0079-word-search
0098-validate-binary-search-tree
0100-same-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0133-clone-graph
0144-binary-tree-preorder-traversal
0200-number-of-islands
0211-design-add-and-search-words-data-structure
0417-pacific-atlantic-water-flow
0572-subtree-of-another-tree
0695-max-area-of-island
0733-flood-fill
0813-all-paths-from-source-to-target
0871-keys-and-rooms
0904-leaf-similar-trees
2121-find-if-path-exists-in-graph

Breadth-First Search

0100-same-tree
0104-maximum-depth-of-binary-tree
0133-clone-graph
0200-number-of-islands
0322-coin-change
0417-pacific-atlantic-water-flow
0695-max-area-of-island
0733-flood-fill
0813-all-paths-from-source-to-target
0871-keys-and-rooms
1036-rotting-oranges
2038-nearest-exit-from-entrance-in-maze
2121-find-if-path-exists-in-graph

Binary Tree

0098-validate-binary-search-tree
0100-same-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0144-binary-tree-preorder-traversal
0450-delete-node-in-a-bst
0572-subtree-of-another-tree
0783-search-in-a-binary-search-tree
0904-leaf-similar-trees

Binary Search Tree

0098-validate-binary-search-tree
0450-delete-node-in-a-bst
0783-search-in-a-binary-search-tree

Backtracking

0017-letter-combinations-of-a-phone-number
0039-combination-sum
0079-word-search
0813-all-paths-from-source-to-target

Enumeration

2337-remove-digit-from-number-to-maximize-result
2844-sum-of-squares-of-special-elements
3221-find-the-peaks

Graph

0133-clone-graph
0813-all-paths-from-source-to-target
0871-keys-and-rooms
2121-find-if-path-exists-in-graph

Database

1908-recyclable-and-low-fat-products

Counting Sort

0561-array-partition
1217-relative-sort-array
2148-minimum-number-of-moves-to-seat-everyone

Number Theory

0258-add-digits

Doubly-Linked List

1582-design-browser-history

Union Find

0128-longest-consecutive-sequence
0200-number-of-islands
0695-max-area-of-island
2121-find-if-path-exists-in-graph

Hash Function

0572-subtree-of-another-tree

Bucket Sort

0347-top-k-frequent-elements

Brainteaser

1086-divisor-game

Game Theory

1086-divisor-game