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

LeetCode Topics

Array

Problem Name	Difficulty
0001-two-sum
0004-median-of-two-sorted-arrays
0015-3sum
0016-3sum-closest
0018-4sum
0026-remove-duplicates-from-sorted-array
0031-next-permutation
0033-search-in-rotated-sorted-array
0037-sudoku-solver
0039-combination-sum
0040-combination-sum-ii
0041-first-missing-positive
0042-trapping-rain-water
0045-jump-game-ii
0046-permutations
0047-permutations-ii
0048-rotate-image
0049-group-anagrams
0051-n-queens
0053-maximum-subarray
0055-jump-game
0056-merge-intervals
0057-insert-interval
0063-unique-paths-ii
0064-minimum-path-sum
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0075-sort-colors
0078-subsets
0081-search-in-rotated-sorted-array-ii
0085-maximal-rectangle
0088-merge-sorted-array
0090-subsets-ii
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0118-pascals-triangle
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
0128-longest-consecutive-sequence
0130-surrounded-regions
0135-candy
0140-word-break-ii
0152-maximum-product-subarray
0167-two-sum-ii-input-array-is-sorted
0169-majority-element
0188-best-time-to-buy-and-sell-stock-iv
0198-house-robber
0200-number-of-islands
0204-count-primes
0209-minimum-size-subarray-sum
0213-house-robber-ii
0215-kth-largest-element-in-an-array
0221-maximal-square
0229-majority-element-ii
0238-product-of-array-except-self
0239-sliding-window-maximum
0240-search-a-2d-matrix-ii
0268-missing-number
0287-find-the-duplicate-number
0300-longest-increasing-subsequence
0303-range-sum-query-immutable
0307-range-sum-query-mutable
0309-best-time-to-buy-and-sell-stock-with-cooldown
0312-burst-balloons
0322-coin-change
0347-top-k-frequent-elements
0368-largest-divisible-subset
0373-find-k-pairs-with-smallest-sums
0403-frog-jump
0416-partition-equal-subset-sum
0417-pacific-atlantic-water-flow
0421-maximum-xor-of-two-numbers-in-an-array
0435-non-overlapping-intervals
0442-find-all-duplicates-in-an-array
0448-find-all-numbers-disappeared-in-an-array
0454-4sum-ii
0455-assign-cookies
0463-island-perimeter
0485-max-consecutive-ones
0493-reverse-pairs
0494-target-sum
0496-next-greater-element-i
0502-ipo
0503-next-greater-element-ii
0518-coin-change-ii
0523-continuous-subarray-sum
0540-single-element-in-a-sorted-array
0542-01-matrix
0560-subarray-sum-equals-k
0621-task-scheduler
0628-maximum-product-of-three-numbers
0630-course-schedule-iii
0632-smallest-range-covering-elements-from-k-lists
0673-number-of-longest-increasing-subsequence
0697-degree-of-an-array
0713-subarray-product-less-than-k
0714-best-time-to-buy-and-sell-stock-with-transaction-fee
0721-accounts-merge
0733-flood-fill
0735-asteroid-collision	Medium
0739-daily-temperatures
0747-min-cost-climbing-stairs
0794-swim-in-rising-water
0823-split-array-with-same-average
0827-making-a-large-island
0854-making-a-large-island
0876-hand-of-straights
0890-lemonade-change
0907-koko-eating-bananas
0924-fair-candy-swap
0945-snakes-and-ladders
0954-maximum-sum-circular-subarray
0966-binary-subarrays-with-sum
0967-minimum-falling-path-sum
0971-shortest-bridge
0980-find-the-shortest-superstring
0994-rotting-oranges
1014-k-closest-points-to-origin
1022-unique-paths-iii
1034-subarrays-with-k-different-integers
1036-rotting-oranges
1037-minimum-number-of-k-consecutive-bit-flips
1046-max-consecutive-ones-iii
1050-construct-binary-search-tree-from-preorder-traversal
1073-number-of-enclaves
1091-shortest-path-in-binary-matrix
1104-coloring-a-border
1117-as-far-from-land-as-possible
1127-last-stone-weight
1129-longest-string-chain
1138-grumpy-bookstore-owner
1171-shortest-path-in-binary-matrix
1256-rank-transform-of-an-array
1294-range-frequency-queries
1319-unique-number-of-occurrences
1335-maximum-candies-allocated-to-k-children
1352-maximum-profit-in-job-scheduling
1370-count-number-of-nice-subarrays
1380-number-of-closed-islands
1402-count-square-submatrices-with-all-ones
1422-divide-array-in-sets-of-k-consecutive-numbers
1424-maximum-candies-you-can-get-from-boxes
1451-minimum-number-of-taps-to-open-to-water-a-garden
1478-maximum-number-of-events-that-can-be-attended
1503-reducing-dishes
1510-find-lucky-integer-in-an-array
1514-minimum-value-to-get-positive-step-by-step-sum
1559-cherry-pickup-ii
1586-longest-subarray-of-1s-after-deleting-one-element
1603-running-sum-of-1d-array
1620-check-if-array-pairs-are-divisible-by-k
1631-path-with-minimum-effort
1663-detect-cycles-in-2d-grid
1669-minimum-cost-to-cut-a-stick
1706-min-cost-to-connect-all-points
1753-path-with-minimum-effort
1826-maximum-xor-with-an-element-from-array
1829-maximum-units-on-a-truck
1830-count-good-meals
1851-maximum-number-of-events-that-can-be-attended-ii
1925-count-nice-pairs-in-an-array
1995-finding-pairs-with-a-certain-sum
2015-determine-whether-matrix-can-be-obtained-by-rotation
2106-find-greatest-common-divisor-of-array
2144-maximum-difference-between-increasing-elements
2160-minimum-operations-to-make-a-uni-value-grid
2162-partition-array-into-two-arrays-to-minimize-sum-difference
2188-minimized-maximum-of-products-distributed-to-any-store
2215-finding-3-digit-even-numbers
2220-find-all-possible-recipes-from-given-supplies
2308-divide-array-into-equal-pairs
2360-substring-with-largest-variance
2375-minimum-obstacle-removal-to-reach-corner
2387-partition-array-such-that-maximum-difference-is-k
2394-count-subarrays-with-score-less-than-k
2469-longest-subsequence-with-limited-sum
2478-longest-nice-subarray
2479-meeting-rooms-iii
2482-maximum-rows-covered-by-columns
2525-count-number-of-distinct-integers-after-reverse-operations
2529-range-product-queries-of-powers
2552-maximum-sum-of-distinct-subarrays-with-length-k
2554-minimum-total-distance-traveled
2591-frog-jump-ii
2609-distinct-prime-factors-of-product-of-array
2720-minimize-the-maximum-difference-of-pairs
2722-prime-in-diagonal
2847-find-maximum-number-of-string-pairs
3214-maximize-area-of-square-hole-in-grid
3227-find-missing-and-repeated-values
3241-divide-array-into-arrays-with-max-difference
3269-number-of-subarrays-that-match-a-pattern-i
3307-find-the-maximum-sum-of-node-values
3321-type-of-triangle
3348-minimum-cost-walk-in-weighted-graph
3416-sum-of-digit-differences-of-all-pairs
3427-special-array-ii
3430-count-days-without-meetings
3442-maximum-total-reward-using-operations-i
3443-maximum-total-reward-using-operations-ii
3461-find-the-minimum-area-to-cover-all-ones-i
3475-minimum-operations-to-make-binary-array-elements-equal-to-one-i
3477-minimum-operations-to-make-binary-array-elements-equal-to-one-ii
3639-zero-array-transformation-i
3647-zero-array-transformation-iii
3657-check-if-grid-can-be-cut-into-sections
3737-count-subarrays-with-majority-element-i
3739-count-subarrays-with-majority-element-ii
3741-reschedule-meetings-for-maximum-free-time-ii
3747-maximum-difference-between-adjacent-elements-in-a-circular-array
3788-maximum-unique-subarray-sum-after-deletion
3809-properties-graph
3837-grid-teleportation-traversal
3842-number-of-ways-to-assign-edge-weights-ii
3843-partition-array-into-two-equal-product-subsets
3847-minimum-swaps-to-sort-by-digit-sum
3884-minimum-absolute-difference-in-sliding-submatrix
3980-best-time-to-buy-and-sell-stock-using-strategy

Depth-First Search

Problem Name	Difficulty
0099-recover-binary-search-tree
0112-path-sum
0113-path-sum-ii
0130-surrounded-regions
0133-clone-graph
0200-number-of-islands
0207-course-schedule
0210-course-schedule-ii
0230-kth-smallest-element-in-a-bst
0386-lexicographical-numbers
0417-pacific-atlantic-water-flow
0437-path-sum-iii
0463-island-perimeter
0547-number-of-provinces
0653-two-sum-iv-input-is-a-bst
0669-trim-a-binary-search-tree
0721-accounts-merge
0733-flood-fill
0744-network-delay-time
0787-cheapest-flights-within-k-stops
0794-swim-in-rising-water
0801-is-graph-bipartite
0802-find-eventual-safe-states
0803-cheapest-flights-within-k-stops
0820-find-eventual-safe-states
0827-making-a-large-island
0854-making-a-large-island
0863-all-nodes-distance-k-in-binary-tree
0871-keys-and-rooms
0947-most-stones-removed-with-same-row-or-column
0971-shortest-bridge
0984-most-stones-removed-with-same-row-or-column
1073-number-of-enclaves
1104-coloring-a-border
1120-flower-planting-with-no-adjacent
1192-critical-connections-in-a-network
1300-critical-connections-in-a-network
1319-number-of-operations-to-make-network-connected
1380-number-of-closed-islands
1442-number-of-operations-to-make-network-connected
1462-course-schedule-iv
1493-frog-position-after-t-seconds
1631-path-with-minimum-effort
1663-detect-cycles-in-2d-grid
1753-path-with-minimum-effort
2403-count-unreachable-pairs-of-nodes-in-an-undirected-graph
2438-find-closest-node-to-given-two-nodes
2461-amount-of-time-for-binary-tree-to-be-infected
2793-count-the-number-of-complete-components
3633-maximize-the-number-of-target-nodes-after-connecting-trees-i
3645-maximize-the-number-of-target-nodes-after-connecting-trees-ii
3809-properties-graph
3842-number-of-ways-to-assign-edge-weights-ii

Breadth-First Search

Problem Name	Difficulty
0112-path-sum
0126-word-ladder-ii
0127-word-ladder
0130-surrounded-regions
0133-clone-graph
0200-number-of-islands
0207-course-schedule
0210-course-schedule-ii
0279-perfect-squares
0322-coin-change
0417-pacific-atlantic-water-flow
0463-island-perimeter
0542-01-matrix
0547-number-of-provinces
0653-two-sum-iv-input-is-a-bst
0721-accounts-merge
0733-flood-fill
0744-network-delay-time
0787-cheapest-flights-within-k-stops
0794-swim-in-rising-water
0801-is-graph-bipartite
0802-find-eventual-safe-states
0803-cheapest-flights-within-k-stops
0820-find-eventual-safe-states
0827-making-a-large-island
0854-making-a-large-island
0863-all-nodes-distance-k-in-binary-tree
0871-keys-and-rooms
0945-snakes-and-ladders
0971-shortest-bridge
0994-rotting-oranges
1036-rotting-oranges
1073-number-of-enclaves
1091-shortest-path-in-binary-matrix
1104-coloring-a-border
1117-as-far-from-land-as-possible
1120-flower-planting-with-no-adjacent
1171-shortest-path-in-binary-matrix
1319-number-of-operations-to-make-network-connected
1380-number-of-closed-islands
1424-maximum-candies-you-can-get-from-boxes
1442-number-of-operations-to-make-network-connected
1462-course-schedule-iv
1493-frog-position-after-t-seconds
1631-path-with-minimum-effort
1663-detect-cycles-in-2d-grid
1753-path-with-minimum-effort
2375-minimum-obstacle-removal-to-reach-corner
2403-count-unreachable-pairs-of-nodes-in-an-undirected-graph
2461-amount-of-time-for-binary-tree-to-be-infected
2793-count-the-number-of-complete-components
3633-maximize-the-number-of-target-nodes-after-connecting-trees-i
3645-maximize-the-number-of-target-nodes-after-connecting-trees-ii
3809-properties-graph
3837-grid-teleportation-traversal

Matrix

Problem Name	Difficulty
0037-sudoku-solver
0048-rotate-image
0063-unique-paths-ii
0064-minimum-path-sum
0073-set-matrix-zeroes
0074-search-a-2d-matrix
0085-maximal-rectangle
0130-surrounded-regions
0200-number-of-islands
0221-maximal-square
0240-search-a-2d-matrix-ii
0417-pacific-atlantic-water-flow
0463-island-perimeter
0542-01-matrix
0733-flood-fill
0794-swim-in-rising-water
0827-making-a-large-island
0854-making-a-large-island
0945-snakes-and-ladders
0967-minimum-falling-path-sum
0971-shortest-bridge
0994-rotting-oranges
1022-unique-paths-iii
1036-rotting-oranges
1073-number-of-enclaves
1091-shortest-path-in-binary-matrix
1104-coloring-a-border
1117-as-far-from-land-as-possible
1171-shortest-path-in-binary-matrix
1380-number-of-closed-islands
1402-count-square-submatrices-with-all-ones
1559-cherry-pickup-ii
1631-path-with-minimum-effort
1663-detect-cycles-in-2d-grid
1753-path-with-minimum-effort
2015-determine-whether-matrix-can-be-obtained-by-rotation
2160-minimum-operations-to-make-a-uni-value-grid
2375-minimum-obstacle-removal-to-reach-corner
2482-maximum-rows-covered-by-columns
2722-prime-in-diagonal
3227-find-missing-and-repeated-values
3461-find-the-minimum-area-to-cover-all-ones-i
3837-grid-teleportation-traversal
3884-minimum-absolute-difference-in-sliding-submatrix

Union Find

Problem Name	Difficulty
0128-longest-consecutive-sequence
0130-surrounded-regions
0200-number-of-islands
0547-number-of-provinces
0721-accounts-merge
0794-swim-in-rising-water
0801-is-graph-bipartite
0827-making-a-large-island
0854-making-a-large-island
0947-most-stones-removed-with-same-row-or-column
0984-most-stones-removed-with-same-row-or-column
1058-lexicographically-smallest-equivalent-string
1073-number-of-enclaves
1319-number-of-operations-to-make-network-connected
1380-number-of-closed-islands
1442-number-of-operations-to-make-network-connected
1631-path-with-minimum-effort
1663-detect-cycles-in-2d-grid
1706-min-cost-to-connect-all-points
1753-path-with-minimum-effort
2403-count-unreachable-pairs-of-nodes-in-an-undirected-graph
2793-count-the-number-of-complete-components
3348-minimum-cost-walk-in-weighted-graph
3809-properties-graph

Graph

Problem Name	Difficulty
0133-clone-graph
0207-course-schedule
0210-course-schedule-ii
0547-number-of-provinces
0744-network-delay-time
0787-cheapest-flights-within-k-stops
0801-is-graph-bipartite
0802-find-eventual-safe-states
0803-cheapest-flights-within-k-stops
0820-find-eventual-safe-states
0871-keys-and-rooms
0947-most-stones-removed-with-same-row-or-column
0984-most-stones-removed-with-same-row-or-column
1120-flower-planting-with-no-adjacent
1192-critical-connections-in-a-network
1300-critical-connections-in-a-network
1319-number-of-operations-to-make-network-connected
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1424-maximum-candies-you-can-get-from-boxes
1442-number-of-operations-to-make-network-connected
1456-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1462-course-schedule-iv
1493-frog-position-after-t-seconds
1706-min-cost-to-connect-all-points
1916-find-center-of-star-graph
1976-number-of-ways-to-arrive-at-destination
2090-number-of-ways-to-arrive-at-destination
2220-find-all-possible-recipes-from-given-supplies
2375-minimum-obstacle-removal-to-reach-corner
2403-count-unreachable-pairs-of-nodes-in-an-undirected-graph
2438-find-closest-node-to-given-two-nodes
2793-count-the-number-of-complete-components
3348-minimum-cost-walk-in-weighted-graph
3809-properties-graph

Minimum Spanning Tree

Problem Name	Difficulty
1706-min-cost-to-connect-all-points

Hash Table

Problem Name	Difficulty
0001-two-sum
0003-longest-substring-without-repeating-characters
0012-integer-to-roman
0013-roman-to-integer
0017-letter-combinations-of-a-phone-number
0037-sudoku-solver
0041-first-missing-positive
0049-group-anagrams
0073-set-matrix-zeroes
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0126-word-ladder-ii
0127-word-ladder
0128-longest-consecutive-sequence
0133-clone-graph
0138-copy-list-with-random-pointer
0140-word-break-ii
0141-linked-list-cycle
0142-linked-list-cycle-ii
0146-lru-cache
0160-intersection-of-two-linked-lists
0169-majority-element
0202-happy-number
0208-implement-trie-prefix-tree
0229-majority-element-ii
0242-valid-anagram
0268-missing-number
0347-top-k-frequent-elements
0355-design-twitter
0387-first-unique-character-in-a-string
0421-maximum-xor-of-two-numbers-in-an-array
0424-longest-repeating-character-replacement
0442-find-all-duplicates-in-an-array
0448-find-all-numbers-disappeared-in-an-array
0451-sort-characters-by-frequency
0454-4sum-ii
0496-next-greater-element-i
0523-continuous-subarray-sum
0560-subarray-sum-equals-k
0621-task-scheduler
0632-smallest-range-covering-elements-from-k-lists
0653-two-sum-iv-input-is-a-bst
0697-degree-of-an-array
0721-accounts-merge
0778-reorganize-string
0863-all-nodes-distance-k-in-binary-tree
0876-hand-of-straights
0924-fair-candy-swap
0947-most-stones-removed-with-same-row-or-column
0966-binary-subarrays-with-sum
0984-most-stones-removed-with-same-row-or-column
1034-subarrays-with-k-different-integers
1129-longest-string-chain
1256-rank-transform-of-an-array
1294-range-frequency-queries
1319-unique-number-of-occurrences
1370-count-number-of-nice-subarrays
1422-divide-array-in-sets-of-k-consecutive-numbers
1460-number-of-substrings-containing-all-three-characters
1510-find-lucky-integer-in-an-array
1620-check-if-array-pairs-are-divisible-by-k
1777-determine-if-two-strings-are-close
1830-count-good-meals
1925-count-nice-pairs-in-an-array
1995-finding-pairs-with-a-certain-sum
2215-finding-3-digit-even-numbers
2220-find-all-possible-recipes-from-given-supplies
2308-divide-array-into-equal-pairs
2461-amount-of-time-for-binary-tree-to-be-infected
2479-meeting-rooms-iii
2520-using-a-robot-to-print-the-lexicographically-smallest-string
2525-count-number-of-distinct-integers-after-reverse-operations
2552-maximum-sum-of-distinct-subarrays-with-length-k
2609-distinct-prime-factors-of-product-of-array
2847-find-maximum-number-of-string-pairs
3227-find-missing-and-repeated-values
3360-minimum-deletions-to-make-string-k-special
3416-sum-of-digit-differences-of-all-pairs
3445-lexicographically-minimum-string-after-removing-stars
3569-count-of-substrings-containing-every-vowel-and-k-consonants-ii
3737-count-subarrays-with-majority-element-i
3739-count-subarrays-with-majority-element-ii
3753-maximum-difference-between-even-and-odd-frequency-i
3754-maximum-manhattan-distance-after-k-changes
3788-maximum-unique-subarray-sum-after-deletion
3809-properties-graph
3837-grid-teleportation-traversal
3847-minimum-swaps-to-sort-by-digit-sum

String

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters
0005-longest-palindromic-substring
0010-regular-expression-matching
0012-integer-to-roman
0013-roman-to-integer
0014-longest-common-prefix
0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0028-find-the-index-of-the-first-occurrence-in-a-string
0038-count-and-say
0044-wildcard-matching
0049-group-anagrams
0072-edit-distance
0115-distinct-subsequences
0125-valid-palindrome
0126-word-ladder-ii
0127-word-ladder
0131-palindrome-partitioning
0132-palindrome-partitioning-ii
0140-word-break-ii
0208-implement-trie-prefix-tree
0214-shortest-palindrome
0241-different-ways-to-add-parentheses
0242-valid-anagram
0387-first-unique-character-in-a-string
0424-longest-repeating-character-replacement
0451-sort-characters-by-frequency
0516-longest-palindromic-subsequence
0583-delete-operation-for-two-strings
0678-valid-parenthesis-string
0680-valid-palindrome-ii
0686-repeated-string-match
0721-accounts-merge
0778-reorganize-string
0957-minimum-add-to-make-parentheses-valid
0980-find-the-shortest-superstring
1058-lexicographically-smallest-equivalent-string
1129-longest-string-chain
1170-shortest-common-supersequence
1197-parsing-a-boolean-expression
1250-longest-common-subsequence
1302-delete-characters-to-make-fancy-string
1403-palindrome-partitioning-iii
1437-minimum-insertion-steps-to-make-a-string-palindrome
1460-number-of-substrings-containing-all-three-characters
1508-longest-happy-prefix
1777-determine-if-two-strings-are-close
1818-maximum-score-from-removing-substrings
1871-palindrome-partitioning-iv
2220-find-all-possible-recipes-from-given-supplies
2260-divide-a-string-into-groups-of-size-k
2346-largest-3-same-digit-number-in-string
2520-using-a-robot-to-print-the-lexicographically-smallest-string
2576-minimum-penalty-for-a-shop
2580-circular-sentence
2847-find-maximum-number-of-string-pairs
3245-find-beautiful-indices-in-the-given-array-i
3303-find-beautiful-indices-in-the-given-array-ii
3360-minimum-deletions-to-make-string-k-special
3445-lexicographically-minimum-string-after-removing-stars
3569-count-of-substrings-containing-every-vowel-and-k-consonants-ii
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
3860-resulting-string-after-adjacent-removals
3867-lexicographically-smallest-string-after-adjacent-removals
3939-process-string-with-special-operations-ii

Dynamic Programming

Problem Name	Difficulty
0005-longest-palindromic-substring
0010-regular-expression-matching
0022-generate-parentheses
0042-trapping-rain-water
0044-wildcard-matching
0045-jump-game-ii
0053-maximum-subarray
0055-jump-game
0062-unique-paths
0063-unique-paths-ii
0064-minimum-path-sum
0070-climbing-stairs
0072-edit-distance
0085-maximal-rectangle
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0115-distinct-subsequences
0118-pascals-triangle
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
0131-palindrome-partitioning
0132-palindrome-partitioning-ii
0140-word-break-ii
0152-maximum-product-subarray
0188-best-time-to-buy-and-sell-stock-iv
0198-house-robber
0213-house-robber-ii
0221-maximal-square
0241-different-ways-to-add-parentheses
0279-perfect-squares
0300-longest-increasing-subsequence
0309-best-time-to-buy-and-sell-stock-with-cooldown
0312-burst-balloons
0322-coin-change
0368-largest-divisible-subset
0403-frog-jump
0416-partition-equal-subset-sum
0435-non-overlapping-intervals
0494-target-sum
0516-longest-palindromic-subsequence
0518-coin-change-ii
0542-01-matrix
0583-delete-operation-for-two-strings
0650-2-keys-keyboard
0673-number-of-longest-increasing-subsequence
0678-valid-parenthesis-string
0688-knight-probability-in-chessboard
0714-best-time-to-buy-and-sell-stock-with-transaction-fee
0747-min-cost-climbing-stairs
0787-cheapest-flights-within-k-stops
0803-cheapest-flights-within-k-stops
0823-split-array-with-same-average
0954-maximum-sum-circular-subarray
0967-minimum-falling-path-sum
0980-find-the-shortest-superstring
1013-fibonacci-number
1117-as-far-from-land-as-possible
1129-longest-string-chain
1170-shortest-common-supersequence
1236-n-th-tribonacci-number
1250-longest-common-subsequence
1263-number-of-dice-rolls-with-target-sum
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1352-maximum-profit-in-job-scheduling
1402-count-square-submatrices-with-all-ones
1403-palindrome-partitioning-iii
1437-minimum-insertion-steps-to-make-a-string-palindrome
1451-minimum-number-of-taps-to-open-to-water-a-garden
1456-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1503-reducing-dishes
1527-number-of-ways-to-paint-n-3-grid
1559-cherry-pickup-ii
1586-longest-subarray-of-1s-after-deleting-one-element
1669-minimum-cost-to-cut-a-stick
1851-maximum-number-of-events-that-can-be-attended-ii
1871-palindrome-partitioning-iv
1976-number-of-ways-to-arrive-at-destination
2061-painting-a-grid-with-three-different-colors
2090-number-of-ways-to-arrive-at-destination
2162-partition-array-into-two-arrays-to-minimize-sum-difference
2360-substring-with-largest-variance
2554-minimum-total-distance-traveled
2882-ways-to-express-an-integer-as-sum-of-powers
3307-find-the-maximum-sum-of-node-values
3442-maximum-total-reward-using-operations-i
3443-maximum-total-reward-using-operations-ii
3477-minimum-operations-to-make-binary-array-elements-equal-to-one-ii
3842-number-of-ways-to-assign-edge-weights-ii
3867-lexicographically-smallest-string-after-adjacent-removals

Backtracking

Problem Name	Difficulty
0017-letter-combinations-of-a-phone-number
0022-generate-parentheses
0037-sudoku-solver
0039-combination-sum
0040-combination-sum-ii
0046-permutations
0047-permutations-ii
0051-n-queens
0052-n-queens-ii
0078-subsets
0090-subsets-ii
0095-unique-binary-search-trees-ii
0113-path-sum-ii
0126-word-ladder-ii
0131-palindrome-partitioning
0140-word-break-ii
0494-target-sum
1022-unique-paths-iii
2482-maximum-rows-covered-by-columns

Trie

Problem Name	Difficulty
0014-longest-common-prefix
0140-word-break-ii
0208-implement-trie-prefix-tree
0386-lexicographical-numbers
0421-maximum-xor-of-two-numbers-in-an-array
0440-k-th-smallest-in-lexicographical-order
1826-maximum-xor-with-an-element-from-array

Memoization

Problem Name	Difficulty
0070-climbing-stairs
0140-word-break-ii
0241-different-ways-to-add-parentheses
1013-fibonacci-number
1236-n-th-tribonacci-number

Math

Problem Name	Difficulty
0002-add-two-numbers
0009-palindrome-number
0012-integer-to-roman
0013-roman-to-integer
0048-rotate-image
0050-powx-n
0060-permutation-sequence
0062-unique-paths
0070-climbing-stairs
0096-unique-binary-search-trees
0202-happy-number
0204-count-primes
0241-different-ways-to-add-parentheses
0263-ugly-number
0268-missing-number
0279-perfect-squares
0326-power-of-three
0368-largest-divisible-subset
0372-super-pow
0400-nth-digit
0507-perfect-number
0523-continuous-subarray-sum
0628-maximum-product-of-three-numbers
0650-2-keys-keyboard
0823-split-array-with-same-average
1013-fibonacci-number
1014-k-closest-points-to-origin
1236-n-th-tribonacci-number
1370-count-number-of-nice-subarrays
1925-count-nice-pairs-in-an-array
2106-find-greatest-common-divisor-of-array
2139-minimum-moves-to-reach-target-score
2160-minimum-operations-to-make-a-uni-value-grid
2202-sum-of-k-mirror-numbers
2525-count-number-of-distinct-integers-after-reverse-operations
2595-smallest-value-after-replacing-with-sum-of-prime-factors
2609-distinct-prime-factors-of-product-of-array
2704-maximum-difference-by-remapping-a-digit
2722-prime-in-diagonal
3201-distribute-candies-among-children-ii
3227-find-missing-and-repeated-values
3321-type-of-triangle
3416-sum-of-digit-differences-of-all-pairs
3682-count-the-number-of-arrays-with-k-matching-adjacent-elements
3754-maximum-manhattan-distance-after-k-changes
3842-number-of-ways-to-assign-edge-weights-ii

Tree

Problem Name	Difficulty
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0099-recover-binary-search-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0112-path-sum
0113-path-sum-ii
0173-binary-search-tree-iterator
0230-kth-smallest-element-in-a-bst
0437-path-sum-iii
0450-delete-node-in-a-bst
0653-two-sum-iv-input-is-a-bst
0669-trim-a-binary-search-tree
0863-all-nodes-distance-k-in-binary-tree
1050-construct-binary-search-tree-from-preorder-traversal
1493-frog-position-after-t-seconds
2461-amount-of-time-for-binary-tree-to-be-infected
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
3842-number-of-ways-to-assign-edge-weights-ii

Binary Search Tree

Problem Name	Difficulty
0004-median-of-two-sorted-arrays
0033-search-in-rotated-sorted-array
0074-search-a-2d-matrix
0081-search-in-rotated-sorted-array-ii
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0099-recover-binary-search-tree
0167-two-sum-ii-input-array-is-sorted
0173-binary-search-tree-iterator
0209-minimum-size-subarray-sum
0230-kth-smallest-element-in-a-bst
0240-search-a-2d-matrix-ii
0268-missing-number
0278-first-bad-version
0287-find-the-duplicate-number
0300-longest-increasing-subsequence
0400-nth-digit
0450-delete-node-in-a-bst
0493-reverse-pairs
0540-single-element-in-a-sorted-array
0653-two-sum-iv-input-is-a-bst
0669-trim-a-binary-search-tree
0713-subarray-product-less-than-k
0794-swim-in-rising-water
0907-koko-eating-bananas
0924-fair-candy-swap
1046-max-consecutive-ones-iii
1050-construct-binary-search-tree-from-preorder-traversal
1294-range-frequency-queries
1335-maximum-candies-allocated-to-k-children
1352-maximum-profit-in-job-scheduling
1631-path-with-minimum-effort
1753-path-with-minimum-effort
1851-maximum-number-of-events-that-can-be-attended-ii
2162-partition-array-into-two-arrays-to-minimize-sum-difference
2188-minimized-maximum-of-products-distributed-to-any-store
2394-count-subarrays-with-score-less-than-k
2469-longest-subsequence-with-limited-sum
2591-frog-jump-ii
2720-minimize-the-maximum-difference-of-pairs
3245-find-beautiful-indices-in-the-given-array-i
3303-find-beautiful-indices-in-the-given-array-ii
3427-special-array-ii

Binary Tree

Problem Name	Difficulty
0095-unique-binary-search-trees-ii
0096-unique-binary-search-trees
0099-recover-binary-search-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0112-path-sum
0113-path-sum-ii
0173-binary-search-tree-iterator
0230-kth-smallest-element-in-a-bst
0437-path-sum-iii
0450-delete-node-in-a-bst
0653-two-sum-iv-input-is-a-bst
0669-trim-a-binary-search-tree
0863-all-nodes-distance-k-in-binary-tree
1050-construct-binary-search-tree-from-preorder-traversal
2461-amount-of-time-for-binary-tree-to-be-infected

Two Pointers

Problem Name	Difficulty
0005-longest-palindromic-substring
0015-3sum
0016-3sum-closest
0018-4sum
0019-remove-nth-node-from-end-of-list
0026-remove-duplicates-from-sorted-array
0028-find-the-index-of-the-first-occurrence-in-a-string
0031-next-permutation
0042-trapping-rain-water
0061-rotate-list
0075-sort-colors
0088-merge-sorted-array
0125-valid-palindrome
0141-linked-list-cycle
0142-linked-list-cycle-ii
0160-intersection-of-two-linked-lists
0167-two-sum-ii-input-array-is-sorted
0202-happy-number
0234-palindrome-linked-list
0287-find-the-duplicate-number
0295-find-median-from-data-stream
0455-assign-cookies
0653-two-sum-iv-input-is-a-bst
0680-valid-palindrome-ii
0908-middle-of-the-linked-list
1129-longest-string-chain
2162-partition-array-into-two-arrays-to-minimize-sum-difference
3245-find-beautiful-indices-in-the-given-array-i
3303-find-beautiful-indices-in-the-given-array-ii
3683-find-the-lexicographically-largest-string-from-the-box-i

Stack

Problem Name	Difficulty
0042-trapping-rain-water
0085-maximal-rectangle
0173-binary-search-tree-iterator
0234-palindrome-linked-list
0496-next-greater-element-i
0503-next-greater-element-ii
0678-valid-parenthesis-string
0735-asteroid-collision	Medium
0739-daily-temperatures
0937-online-stock-span
0957-minimum-add-to-make-parentheses-valid
1050-construct-binary-search-tree-from-preorder-traversal
1197-parsing-a-boolean-expression
1818-maximum-score-from-removing-substrings
2520-using-a-robot-to-print-the-lexicographically-smallest-string
3445-lexicographically-minimum-string-after-removing-stars
3860-resulting-string-after-adjacent-removals

Design

Problem Name	Difficulty
0146-lru-cache
0173-binary-search-tree-iterator
0208-implement-trie-prefix-tree
0295-find-median-from-data-stream
0303-range-sum-query-immutable
0307-range-sum-query-mutable
0355-design-twitter
0937-online-stock-span
1294-range-frequency-queries
1995-finding-pairs-with-a-certain-sum

Iterator

Problem Name	Difficulty
0173-binary-search-tree-iterator

Topological Sort

Problem Name	Difficulty
0207-course-schedule
0210-course-schedule-ii
0802-find-eventual-safe-states
0820-find-eventual-safe-states
1462-course-schedule-iv
1976-number-of-ways-to-arrive-at-destination
2090-number-of-ways-to-arrive-at-destination
2220-find-all-possible-recipes-from-given-supplies

Heap (Priority Queue)

Problem Name	Difficulty
0023-merge-k-sorted-lists
0215-kth-largest-element-in-an-array
0239-sliding-window-maximum
0295-find-median-from-data-stream
0347-top-k-frequent-elements
0355-design-twitter
0373-find-k-pairs-with-smallest-sums
0451-sort-characters-by-frequency
0502-ipo
0621-task-scheduler
0630-course-schedule-iii
0632-smallest-range-covering-elements-from-k-lists
0744-network-delay-time
0778-reorganize-string
0787-cheapest-flights-within-k-stops
0794-swim-in-rising-water
0803-cheapest-flights-within-k-stops
1014-k-closest-points-to-origin
1127-last-stone-weight
1478-maximum-number-of-events-that-can-be-attended
1631-path-with-minimum-effort
1753-path-with-minimum-effort
2375-minimum-obstacle-removal-to-reach-corner
2479-meeting-rooms-iii
3445-lexicographically-minimum-string-after-removing-stars
3647-zero-array-transformation-iii

Shortest Path

Problem Name	Difficulty
0744-network-delay-time
0787-cheapest-flights-within-k-stops
0803-cheapest-flights-within-k-stops
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1456-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1976-number-of-ways-to-arrive-at-destination
2090-number-of-ways-to-arrive-at-destination
2375-minimum-obstacle-removal-to-reach-corner

Monotonic Stack

Problem Name	Difficulty
0042-trapping-rain-water
0085-maximal-rectangle
0496-next-greater-element-i
0503-next-greater-element-ii
0739-daily-temperatures
0937-online-stock-span
1050-construct-binary-search-tree-from-preorder-traversal

Biconnected Component

Problem Name	Difficulty
1192-critical-connections-in-a-network
1300-critical-connections-in-a-network

Sliding Window

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters
0209-minimum-size-subarray-sum
0239-sliding-window-maximum
0424-longest-repeating-character-replacement
0632-smallest-range-covering-elements-from-k-lists
0713-subarray-product-less-than-k
0966-binary-subarrays-with-sum
1034-subarrays-with-k-different-integers
1037-minimum-number-of-k-consecutive-bit-flips
1046-max-consecutive-ones-iii
1138-grumpy-bookstore-owner
1370-count-number-of-nice-subarrays
1460-number-of-substrings-containing-all-three-characters
1586-longest-subarray-of-1s-after-deleting-one-element
2394-count-subarrays-with-score-less-than-k
2478-longest-nice-subarray
2552-maximum-sum-of-distinct-subarrays-with-length-k
3475-minimum-operations-to-make-binary-array-elements-equal-to-one-i
3569-count-of-substrings-containing-every-vowel-and-k-consonants-ii
3761-maximum-difference-between-even-and-odd-frequency-ii
3980-best-time-to-buy-and-sell-stock-using-strategy

Prefix Sum

Problem Name	Difficulty
0209-minimum-size-subarray-sum
0238-product-of-array-except-self
0303-range-sum-query-immutable
0523-continuous-subarray-sum
0560-subarray-sum-equals-k
0713-subarray-product-less-than-k
0966-binary-subarrays-with-sum
1037-minimum-number-of-k-consecutive-bit-flips
1046-max-consecutive-ones-iii
1370-count-number-of-nice-subarrays
1514-minimum-value-to-get-positive-step-by-step-sum
1603-running-sum-of-1d-array
2394-count-subarrays-with-score-less-than-k
2469-longest-subsequence-with-limited-sum
2529-range-product-queries-of-powers
2576-minimum-penalty-for-a-shop
3427-special-array-ii
3475-minimum-operations-to-make-binary-array-elements-equal-to-one-i
3639-zero-array-transformation-i
3647-zero-array-transformation-iii
3737-count-subarrays-with-majority-element-i
3739-count-subarrays-with-majority-element-ii
3761-maximum-difference-between-even-and-odd-frequency-ii
3980-best-time-to-buy-and-sell-stock-using-strategy

Combinatorics

Problem Name	Difficulty
0062-unique-paths
3201-distribute-candies-among-children-ii
3682-count-the-number-of-arrays-with-k-matching-adjacent-elements

Recursion

Problem Name	Difficulty
0002-add-two-numbers
0010-regular-expression-matching
0021-merge-two-sorted-lists
0025-reverse-nodes-in-k-group
0044-wildcard-matching
0050-powx-n
0060-permutation-sequence
0206-reverse-linked-list
0234-palindrome-linked-list
0241-different-ways-to-add-parentheses
0326-power-of-three
1013-fibonacci-number
1197-parsing-a-boolean-expression
3843-partition-array-into-two-equal-product-subsets

Greedy

Problem Name	Difficulty
0044-wildcard-matching
0045-jump-game-ii
0055-jump-game
0122-best-time-to-buy-and-sell-stock-ii
0135-candy
0435-non-overlapping-intervals
0455-assign-cookies
0502-ipo
0621-task-scheduler
0630-course-schedule-iii
0632-smallest-range-covering-elements-from-k-lists
0678-valid-parenthesis-string
0680-valid-palindrome-ii
0714-best-time-to-buy-and-sell-stock-with-transaction-fee
0778-reorganize-string
0876-hand-of-straights
0890-lemonade-change
0957-minimum-add-to-make-parentheses-valid
1422-divide-array-in-sets-of-k-consecutive-numbers
1451-minimum-number-of-taps-to-open-to-water-a-garden
1478-maximum-number-of-events-that-can-be-attended
1503-reducing-dishes
1818-maximum-score-from-removing-substrings
1829-maximum-units-on-a-truck
2139-minimum-moves-to-reach-target-score
2188-minimized-maximum-of-products-distributed-to-any-store
2387-partition-array-such-that-maximum-difference-is-k
2469-longest-subsequence-with-limited-sum
2520-using-a-robot-to-print-the-lexicographically-smallest-string
2591-frog-jump-ii
2704-maximum-difference-by-remapping-a-digit
2720-minimize-the-maximum-difference-of-pairs
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
3477-minimum-operations-to-make-binary-array-elements-equal-to-one-ii
3647-zero-array-transformation-iii
3741-reschedule-meetings-for-maximum-free-time-ii
3788-maximum-unique-subarray-sum-after-deletion

Binary Indexed Tree

Problem Name	Difficulty
0307-range-sum-query-mutable
0493-reverse-pairs
0673-number-of-longest-increasing-subsequence

Segment Tree

Problem Name	Difficulty
0307-range-sum-query-mutable
0493-reverse-pairs
0673-number-of-longest-increasing-subsequence
1294-range-frequency-queries
3737-count-subarrays-with-majority-element-i
3739-count-subarrays-with-majority-element-ii

Bit Manipulation

Problem Name	Difficulty
0078-subsets
0090-subsets-ii
0201-bitwise-and-of-numbers-range
0268-missing-number
0287-find-the-duplicate-number
0421-maximum-xor-of-two-numbers-in-an-array
0823-split-array-with-same-average
0980-find-the-shortest-superstring
1022-unique-paths-iii
1037-minimum-number-of-k-consecutive-bit-flips
1826-maximum-xor-with-an-element-from-array
2162-partition-array-into-two-arrays-to-minimize-sum-difference
2308-divide-array-into-equal-pairs
2478-longest-nice-subarray
2482-maximum-rows-covered-by-columns
2529-range-product-queries-of-powers
3307-find-the-maximum-sum-of-node-values
3348-minimum-cost-walk-in-weighted-graph
3443-maximum-total-reward-using-operations-ii
3475-minimum-operations-to-make-binary-array-elements-equal-to-one-i
3843-partition-array-into-two-equal-product-subsets

String Matching

Problem Name	Difficulty
0028-find-the-index-of-the-first-occurrence-in-a-string
0214-shortest-palindrome
0686-repeated-string-match
1508-longest-happy-prefix
3245-find-beautiful-indices-in-the-given-array-i
3269-number-of-subarrays-that-match-a-pattern-i
3303-find-beautiful-indices-in-the-given-array-ii

Rolling Hash

Problem Name	Difficulty
0214-shortest-palindrome
1508-longest-happy-prefix
3245-find-beautiful-indices-in-the-given-array-i
3269-number-of-subarrays-that-match-a-pattern-i
3303-find-beautiful-indices-in-the-given-array-ii

Hash Function

Problem Name	Difficulty
0214-shortest-palindrome
1508-longest-happy-prefix
3245-find-beautiful-indices-in-the-given-array-i
3269-number-of-subarrays-that-match-a-pattern-i
3303-find-beautiful-indices-in-the-given-array-ii

Ordered Set

Problem Name	Difficulty
0493-reverse-pairs
2162-partition-array-into-two-arrays-to-minimize-sum-difference

Bitmask

Problem Name	Difficulty
0823-split-array-with-same-average
0980-find-the-shortest-superstring
2162-partition-array-into-two-arrays-to-minimize-sum-difference

Sorting

Problem Name	Difficulty
0015-3sum
0016-3sum-closest
0018-4sum
0047-permutations-ii
0049-group-anagrams
0056-merge-intervals
0075-sort-colors
0088-merge-sorted-array
0169-majority-element
0215-kth-largest-element-in-an-array
0229-majority-element-ii
0242-valid-anagram
0268-missing-number
0295-find-median-from-data-stream
0347-top-k-frequent-elements
0368-largest-divisible-subset
0435-non-overlapping-intervals
0451-sort-characters-by-frequency
0455-assign-cookies
0502-ipo
0621-task-scheduler
0628-maximum-product-of-three-numbers
0630-course-schedule-iii
0632-smallest-range-covering-elements-from-k-lists
0721-accounts-merge
0778-reorganize-string
0876-hand-of-straights
0924-fair-candy-swap
1014-k-closest-points-to-origin
1129-longest-string-chain
1256-rank-transform-of-an-array
1352-maximum-profit-in-job-scheduling
1422-divide-array-in-sets-of-k-consecutive-numbers
1478-maximum-number-of-events-that-can-be-attended
1503-reducing-dishes
1669-minimum-cost-to-cut-a-stick
1777-determine-if-two-strings-are-close
1829-maximum-units-on-a-truck
1851-maximum-number-of-events-that-can-be-attended-ii
2160-minimum-operations-to-make-a-uni-value-grid
2215-finding-3-digit-even-numbers
2387-partition-array-such-that-maximum-difference-is-k
2469-longest-subsequence-with-limited-sum
2479-meeting-rooms-iii
2554-minimum-total-distance-traveled
3214-maximize-area-of-square-hole-in-grid
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
3430-count-days-without-meetings
3647-zero-array-transformation-iii
3657-check-if-grid-can-be-cut-into-sections
3847-minimum-swaps-to-sort-by-digit-sum
3884-minimum-absolute-difference-in-sliding-submatrix

Divide and Conquer

Problem Name	Difficulty
0004-median-of-two-sorted-arrays
0023-merge-k-sorted-lists
0053-maximum-subarray
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0169-majority-element
0215-kth-largest-element-in-an-array
0240-search-a-2d-matrix-ii
0347-top-k-frequent-elements
0372-super-pow
0493-reverse-pairs
0954-maximum-sum-circular-subarray
1014-k-closest-points-to-origin
3737-count-subarrays-with-majority-element-i
3739-count-subarrays-with-majority-element-ii

Bucket Sort

Problem Name	Difficulty
0347-top-k-frequent-elements
0451-sort-characters-by-frequency

Counting

Problem Name	Difficulty
0169-majority-element
0229-majority-element-ii
0347-top-k-frequent-elements
0387-first-unique-character-in-a-string
0451-sort-characters-by-frequency
0621-task-scheduler
0778-reorganize-string
1034-subarrays-with-k-different-integers
1510-find-lucky-integer-in-an-array
1620-check-if-array-pairs-are-divisible-by-k
1777-determine-if-two-strings-are-close
1925-count-nice-pairs-in-an-array
2308-divide-array-into-equal-pairs
2525-count-number-of-distinct-integers-after-reverse-operations
3360-minimum-deletions-to-make-string-k-special
3416-sum-of-digit-differences-of-all-pairs
3737-count-subarrays-with-majority-element-i
3753-maximum-difference-between-even-and-odd-frequency-i
3754-maximum-manhattan-distance-after-k-changes

Quickselect

Problem Name	Difficulty
0215-kth-largest-element-in-an-array
0347-top-k-frequent-elements
1014-k-closest-points-to-origin

Geometry

Problem Name	Difficulty
1014-k-closest-points-to-origin

Data Stream

Problem Name	Difficulty
0295-find-median-from-data-stream
0937-online-stock-span

Enumeration

Problem Name	Difficulty
0204-count-primes
2202-sum-of-k-mirror-numbers
2215-finding-3-digit-even-numbers
2482-maximum-rows-covered-by-columns
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
3843-partition-array-into-two-equal-product-subsets

Simulation

Problem Name	Difficulty
0735-asteroid-collision	Medium
2260-divide-a-string-into-groups-of-size-k
2479-meeting-rooms-iii
2595-smallest-value-after-replacing-with-sum-of-prime-factors
2847-find-maximum-number-of-string-pairs
3860-resulting-string-after-adjacent-removals
3939-process-string-with-special-operations-ii

Linked List

Problem Name	Difficulty
0002-add-two-numbers
0019-remove-nth-node-from-end-of-list
0021-merge-two-sorted-lists
0023-merge-k-sorted-lists
0025-reverse-nodes-in-k-group
0061-rotate-list
0092-reverse-linked-list-ii
0138-copy-list-with-random-pointer
0141-linked-list-cycle
0142-linked-list-cycle-ii
0146-lru-cache
0160-intersection-of-two-linked-lists
0206-reverse-linked-list
0234-palindrome-linked-list
0237-delete-node-in-a-linked-list
0355-design-twitter
0908-middle-of-the-linked-list

Merge Sort

Problem Name	Difficulty
0023-merge-k-sorted-lists
0493-reverse-pairs
3737-count-subarrays-with-majority-element-i
3739-count-subarrays-with-majority-element-ii

Queue

Problem Name	Difficulty
0239-sliding-window-maximum
0387-first-unique-character-in-a-string
0954-maximum-sum-circular-subarray
1037-minimum-number-of-k-consecutive-bit-flips
3475-minimum-operations-to-make-binary-array-elements-equal-to-one-i

Number Theory

Problem Name	Difficulty
0204-count-primes
2106-find-greatest-common-divisor-of-array
2595-smallest-value-after-replacing-with-sum-of-prime-factors
2609-distinct-prime-factors-of-product-of-array
2722-prime-in-diagonal

Monotonic Queue

Problem Name	Difficulty
0239-sliding-window-maximum
0954-maximum-sum-circular-subarray

Interactive

Problem Name	Difficulty
0278-first-bad-version

Database

Problem Name	Difficulty
0175-combine-two-tables
0176-second-highest-salary
0178-rank-scores
0180-consecutive-numbers
0181-employees-earning-more-than-their-managers
0182-duplicate-emails
0183-customers-who-never-order
0184-department-highest-salary
0196-delete-duplicate-emails
0197-rising-temperature
0262-trips-and-users
0570-managers-with-at-least-5-direct-reports
0577-employee-bonus
0584-find-customer-referee
0585-investments-in-2016
0586-customer-placing-the-largest-number-of-orders
0595-big-countries
0596-classes-with-at-least-5-students
0602-friend-requests-ii-who-has-the-most-friends
0607-sales-person
0608-tree-node
0610-triangle-judgement
0619-biggest-single-number
0620-not-boring-movies
0626-exchange-seats
0627-swap-salary
1135-customers-who-bought-all-products
1136-actors-and-directors-who-cooperated-at-least-three-times
1153-product-sales-analysis-i
1155-product-sales-analysis-iii
1161-project-employees-i
1174-sales-analysis-iii
1179-game-play-analysis-i
1245-user-activity-for-the-past-30-days-i
1258-article-views-i
1268-market-analysis-i
1278-product-price-at-a-given-date
1292-immediate-food-delivery-ii
1301-reformat-department-table
1317-monthly-transactions-i
1327-last-person-to-fit-in-the-bus
1338-queries-quality-and-percentage
1390-average-selling-price
1415-students-and-examinations
1452-restaurant-growth
1462-list-the-products-ordered-in-a-period
1480-movie-rating
1523-capital-gainloss
1908-recyclable-and-low-fat-products
2057-count-salary-categories
2087-confirmation-rate
3530-odd-and-even-transactions
3816-dna-pattern-recognition
3848-analyze-subscription-conversion
3865-find-product-recommendation-pairs
3898-seasonal-sales-analysis
3921-find-consistently-improving-employees
3942-find-drivers-with-improved-fuel-efficiency

Doubly-Linked List

Problem Name	Difficulty
0146-lru-cache

Graph Theory

Problem Name	Difficulty
0787-cheapest-flights-within-k-stops