Leetcode

https://leetcode.com/u/saiei/

Two Pointers

0075-sort-colors
0633-sum-of-square-numbers
0853-most-profit-assigning-work
2572-append-characters-to-string-to-make-subsequence

String

0409-longest-palindrome
0415-add-strings
2021-remove-all-occurrences-of-a-substring
2572-append-characters-to-string-to-make-subsequence

Greedy

0409-longest-palindrome
0853-most-profit-assigning-work
0876-hand-of-straights
2572-append-characters-to-string-to-make-subsequence

Hash Table

0409-longest-palindrome
0876-hand-of-straights
1370-count-number-of-nice-subarrays

Array

0039-combination-sum
0040-combination-sum-ii
0075-sort-colors
0121-best-time-to-buy-and-sell-stock
0853-most-profit-assigning-work
0876-hand-of-straights
0948-sort-an-array
1370-count-number-of-nice-subarrays
1605-minimum-number-of-days-to-make-m-bouquets
1758-distribute-repeating-integers

Sorting

0075-sort-colors
0853-most-profit-assigning-work
0876-hand-of-straights
0948-sort-an-array

Math

0279-perfect-squares
0415-add-strings
0633-sum-of-square-numbers
1370-count-number-of-nice-subarrays

Simulation

0415-add-strings

Dynamic Programming

0121-best-time-to-buy-and-sell-stock
0279-perfect-squares
1758-distribute-repeating-integers

Breadth-First Search

0279-perfect-squares

Binary Search

0633-sum-of-square-numbers
0853-most-profit-assigning-work
1605-minimum-number-of-days-to-make-m-bouquets

Divide and Conquer

0948-sort-an-array

Heap (Priority Queue)

0948-sort-an-array

Merge Sort

0948-sort-an-array

Bucket Sort

0948-sort-an-array

Radix Sort

0948-sort-an-array

Counting Sort

0948-sort-an-array

Backtracking

0039-combination-sum
0040-combination-sum-ii
1758-distribute-repeating-integers

Bit Manipulation

1758-distribute-repeating-integers

Bitmask

1758-distribute-repeating-integers

Sliding Window

1370-count-number-of-nice-subarrays

Linked List

0206-reverse-linked-list

Recursion

0206-reverse-linked-list

LeetCode Topics

Greedy

Problem Name	Difficulty
0134-gas-station
0316-remove-duplicate-letters
0624-maximum-distance-in-arrays
0670-maximum-swap
0890-lemonade-change
0957-minimum-add-to-make-parentheses-valid
1285-balance-a-binary-search-tree
1304-longest-happy-string
1616-minimum-difference-between-largest-and-smallest-value-in-three-moves
1766-minimum-number-of-removals-to-make-mountain-array
1818-maximum-score-from-removing-substrings
2089-maximum-matrix-sum
2095-minimum-number-of-swaps-to-make-the-string-balanced
2139-minimum-moves-to-reach-target-score	Medium
2379-maximum-total-importance-of-roads
2488-divide-intervals-into-minimum-number-of-groups
2616-maximal-score-after-applying-k-operations
2640-maximum-number-of-integers-to-choose-from-a-range-i
2716-prime-subtraction-operation
3195-separate-black-and-white-balls
3276-minimum-number-of-pushes-to-type-word-ii

Graph

Problem Name	Difficulty
0820-find-eventual-safe-states
0984-most-stones-removed-with-same-row-or-column
1325-path-with-maximum-probability
1456-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1485-minimum-cost-to-make-at-least-one-valid-path-in-a-grid
2171-second-minimum-time-to-reach-destination
2201-valid-arrangement-of-pairs
2375-minimum-obstacle-removal-to-reach-corner
2379-maximum-total-importance-of-roads
2711-minimum-time-to-visit-a-cell-in-a-grid
2803-modify-graph-edge-weights
3189-find-champion-ii
3235-minimum-cost-to-convert-string-i
3517-shortest-distance-after-road-addition-queries-i

Sorting

Problem Name	Difficulty
0015-3sum	Medium
0056-merge-intervals	Medium
0075-sort-colors	Medium
0148-sort-list
0215-kth-largest-element-in-an-array	Medium
0268-missing-number	Easy
0347-top-k-frequent-elements	Medium
0350-intersection-of-two-arrays-ii
0539-minimum-time-difference
0719-find-k-th-smallest-pair-distance
0721-accounts-merge	Medium
0726-number-of-atoms
0883-car-fleet
0948-sort-an-array
0987-reveal-cards-in-increasing-order
1029-vertical-order-traversal-of-a-binary-tree
1256-rank-transform-of-an-array
1333-sort-the-jumbled-numbers
1468-check-if-n-and-its-double-exist
1556-make-two-arrays-equal-by-reversing-subarrays
1615-range-sum-of-sorted-subarray-sums
1616-minimum-difference-between-largest-and-smallest-value-in-three-moves
1741-sort-array-by-increasing-frequency
2164-two-best-non-overlapping-events
2179-most-beautiful-item-for-each-query
2379-maximum-total-importance-of-roads
2488-divide-intervals-into-minimum-number-of-groups
2502-sort-the-people
2554-minimum-total-distance-traveled
2581-divide-players-into-teams-of-equal-skill
2586-longest-square-streak-in-an-array
2640-maximum-number-of-integers-to-choose-from-a-range-i
2646-kth-largest-sum-in-a-binary-tree
2695-find-score-of-an-array-after-marking-all-elements
2699-count-the-number-of-fair-pairs
2846-robot-collisions
2891-maximum-beauty-of-an-array-after-applying-operation
3276-minimum-number-of-pushes-to-type-word-ii
3291-find-if-array-can-be-sorted

Heap (Priority Queue)

Problem Name	Difficulty
0215-kth-largest-element-in-an-array	Medium
0239-sliding-window-maximum
0264-ugly-number-ii
0347-top-k-frequent-elements	Medium
0407-trapping-rain-water-ii
0743-network-delay-time	Medium
0789-kth-largest-element-in-a-stream
0892-shortest-subarray-with-sum-at-least-k
0948-sort-an-array
1304-longest-happy-string
1325-path-with-maximum-probability
1485-minimum-cost-to-make-at-least-one-valid-path-in-a-grid
1631-path-with-minimum-effort	Medium
2054-the-number-of-the-smallest-unoccupied-chair
2164-two-best-non-overlapping-events
2375-minimum-obstacle-removal-to-reach-corner
2379-maximum-total-importance-of-roads
2434-design-a-number-container-system
2488-divide-intervals-into-minimum-number-of-groups
2616-maximal-score-after-applying-k-operations
2692-take-gifts-from-the-richest-pile
2695-find-score-of-an-array-after-marking-all-elements
2711-minimum-time-to-visit-a-cell-in-a-grid
2803-modify-graph-edge-weights
3332-minimum-operations-to-exceed-threshold-value-ii

Hash Table

Problem Name	Difficulty
0001-two-sum
0003-longest-substring-without-repeating-characters
0073-set-matrix-zeroes	Medium
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0126-word-ladder-ii	Hard
0127-word-ladder	Hard
0142-linked-list-cycle-ii
0264-ugly-number-ii
0268-missing-number	Easy
0347-top-k-frequent-elements	Medium
0350-intersection-of-two-arrays-ii
0432-all-oone-data-structure
0525-contiguous-array	Medium
0560-subarray-sum-equals-k	Medium
0567-permutation-in-string
0652-find-duplicate-subtrees
0653-two-sum-iv-input-is-a-bst
0721-accounts-merge	Medium
0726-number-of-atoms
0870-magic-squares-in-grid
0906-walking-robot-simulation
0920-uncommon-words-from-two-sentences
0984-most-stones-removed-with-same-row-or-column
0997-find-the-town-judge	Easy
0999-regions-cut-by-slashes
1029-vertical-order-traversal-of-a-binary-tree
1147-flip-columns-for-maximum-number-of-equal-rows
1160-letter-tile-possibilities
1207-delete-nodes-and-return-forest
1256-rank-transform-of-an-array
1267-remove-zero-sum-consecutive-nodes-from-linked-list
1468-check-if-n-and-its-double-exist
1473-find-the-longest-substring-containing-vowels-in-even-counts
1556-make-two-arrays-equal-by-reversing-subarrays
1620-check-if-array-pairs-are-divisible-by-k
1694-make-sum-divisible-by-p
1715-split-a-string-into-the-max-number-of-unique-substrings
1741-sort-array-by-increasing-frequency
1786-count-the-number-of-consistent-strings
2054-the-number-of-the-smallest-unoccupied-chair
2163-kth-distinct-string-in-an-array
2306-create-binary-tree-from-descriptions
2356-largest-combination-with-bitwise-and-greater-than-zero
2434-design-a-number-container-system
2448-count-number-of-bad-pairs
2502-sort-the-people
2552-maximum-sum-of-distinct-subarrays-with-length-k
2581-divide-players-into-teams-of-equal-skill
2586-longest-square-streak-in-an-array
2599-take-k-of-each-character-from-left-and-right
2640-maximum-number-of-integers-to-choose-from-a-range-i
2677-cousins-in-binary-tree-ii
2685-first-completely-painted-row-or-column
2695-find-score-of-an-array-after-marking-all-elements
2755-extra-characters-in-a-string
3005-count-elements-with-maximum-frequency	Easy
3267-find-longest-special-substring-that-occurs-thrice-i
3276-minimum-number-of-pushes-to-type-word-ii
3329-find-the-length-of-the-longest-common-prefix
3501-delete-nodes-from-linked-list-present-in-array

Linked List

Problem Name	Difficulty
0021-merge-two-sorted-lists
0025-reverse-nodes-in-k-group
0061-rotate-list
0142-linked-list-cycle-ii
0148-sort-list
0432-all-oone-data-structure
0725-split-linked-list-in-parts
0859-design-circular-deque
1267-remove-zero-sum-consecutive-nodes-from-linked-list
1484-linked-list-in-binary-tree
2182-find-the-minimum-and-maximum-number-of-nodes-between-critical-points
2299-merge-nodes-in-between-zeros
2411-spiral-matrix-iv
2903-insert-greatest-common-divisors-in-linked-list
3501-delete-nodes-from-linked-list-present-in-array

Two Pointers

Problem Name	Difficulty
0015-3sum	Medium
0026-remove-duplicates-from-sorted-array	Easy
0027-remove-element
0061-rotate-list
0075-sort-colors	Medium
0142-linked-list-cycle-ii
0148-sort-list
0189-rotate-array	Medium
0283-move-zeroes	Easy
0287-find-the-duplicate-number	Medium
0344-reverse-string
0350-intersection-of-two-arrays-ii
0567-permutation-in-string
0653-two-sum-iv-input-is-a-bst
0719-find-k-th-smallest-pair-distance
1468-check-if-n-and-its-double-exist
1566-check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence
1615-range-sum-of-sorted-subarray-sums
1679-shortest-subarray-to-be-removed-to-make-array-sorted
1923-sentence-similarity-iii
1972-rotating-the-box
2095-minimum-number-of-swaps-to-make-the-string-balanced
2414-move-pieces-to-obtain-a-string
2488-divide-intervals-into-minimum-number-of-groups
2581-divide-players-into-teams-of-equal-skill
2699-count-the-number-of-fair-pairs
3018-make-string-a-subsequence-using-cyclic-increments
3195-separate-black-and-white-balls

Recursion

Problem Name	Difficulty
0021-merge-two-sorted-lists
0025-reverse-nodes-in-k-group
0241-different-ways-to-add-parentheses
0273-integer-to-english-words
0394-decode-string
1197-parsing-a-boolean-expression
1951-find-the-winner-of-the-circular-game

Divide and Conquer

Problem Name	Difficulty
0053-maximum-subarray
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0148-sort-list
0215-kth-largest-element-in-an-array	Medium
0347-top-k-frequent-elements	Medium
0948-sort-an-array
1285-balance-a-binary-search-tree

Merge Sort

Problem Name	Difficulty
0148-sort-list
0948-sort-an-array

Array

Problem Name	Difficulty
0001-two-sum
0015-3sum	Medium
0026-remove-duplicates-from-sorted-array	Easy
0027-remove-element
0033-search-in-rotated-sorted-array	Medium
0035-search-insert-position
0040-combination-sum-ii
0048-rotate-image	Medium
0053-maximum-subarray
0054-spiral-matrix	Medium
0056-merge-intervals	Medium
0057-insert-interval	Medium
0064-minimum-path-sum	Medium
0073-set-matrix-zeroes	Medium
0075-sort-colors	Medium
0084-largest-rectangle-in-histogram
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0134-gas-station
0153-find-minimum-in-rotated-sorted-array	Medium
0189-rotate-array	Medium
0200-number-of-islands	Medium
0209-minimum-size-subarray-sum
0215-kth-largest-element-in-an-array	Medium
0238-product-of-array-except-self	Medium
0239-sliding-window-maximum
0268-missing-number	Easy
0283-move-zeroes	Easy
0287-find-the-duplicate-number	Medium
0347-top-k-frequent-elements	Medium
0350-intersection-of-two-arrays-ii
0407-trapping-rain-water-ii
0417-pacific-atlantic-water-flow	Medium
0525-contiguous-array	Medium
0539-minimum-time-difference
0560-subarray-sum-equals-k	Medium
0624-maximum-distance-in-arrays
0643-maximum-average-subarray-i	Easy
0719-find-k-th-smallest-pair-distance
0721-accounts-merge	Medium
0724-find-pivot-index	Easy
0729-my-calendar-i
0731-my-calendar-ii
0733-flood-fill	Easy
0735-asteroid-collision
0739-daily-temperatures
0787-sliding-puzzle
0859-design-circular-deque
0870-magic-squares-in-grid
0883-car-fleet
0890-lemonade-change
0892-shortest-subarray-with-sum-at-least-k
0906-walking-robot-simulation
0909-stone-game
0921-spiral-matrix-iii
0948-sort-an-array
0987-reveal-cards-in-increasing-order
0994-rotting-oranges	Medium
0997-find-the-town-judge	Easy
0999-regions-cut-by-slashes
1002-maximum-width-ramp
1025-minimum-cost-for-tickets
1050-construct-binary-search-tree-from-preorder-traversal
1147-flip-columns-for-maximum-number-of-equal-rows
1196-filling-bookcase-shelves
1207-delete-nodes-and-return-forest
1231-replace-elements-with-greatest-element-on-right-side
1240-stone-game-ii
1256-rank-transform-of-an-array
1306-jump-game-iii	Medium
1325-path-with-maximum-probability
1333-sort-the-jumbled-numbers
1350-remove-sub-folders-from-the-filesystem
1396-count-servers-that-communicate
1402-count-square-submatrices-with-all-ones
1435-xor-queries-of-a-subarray
1468-check-if-n-and-its-double-exist
1477-product-of-the-last-k-numbers
1485-minimum-cost-to-make-at-least-one-valid-path-in-a-grid
1496-lucky-numbers-in-a-matrix
1497-design-a-stack-with-increment-operation
1511-count-number-of-teams
1556-make-two-arrays-equal-by-reversing-subarrays
1615-range-sum-of-sorted-subarray-sums
1616-minimum-difference-between-largest-and-smallest-value-in-three-moves
1620-check-if-array-pairs-are-divisible-by-k
1631-path-with-minimum-effort	Medium
1679-shortest-subarray-to-be-removed-to-make-array-sorted
1691-minimum-number-of-days-to-disconnect-island
1694-make-sum-divisible-by-p
1720-crawler-log-folder
1741-sort-array-by-increasing-frequency
1755-defuse-the-bomb
1766-minimum-number-of-removals-to-make-mountain-array
1786-count-the-number-of-consistent-strings
1803-average-waiting-time
1819-construct-the-lexicographically-largest-valid-sequence
1876-map-of-highest-peak
1886-minimum-limit-of-balls-in-a-bag
1923-sentence-similarity-iii
1940-maximum-xor-for-each-query
1951-find-the-winner-of-the-circular-game
1972-rotating-the-box
2006-find-the-student-that-will-replace-the-chalk
2035-count-sub-islands
2054-the-number-of-the-smallest-unoccupied-chair
2067-maximum-number-of-points-with-cost
2089-maximum-matrix-sum
2145-grid-game
2155-find-missing-observations
2163-kth-distinct-string-in-an-array
2164-two-best-non-overlapping-events
2170-count-number-of-maximum-bitwise-or-subsets
2179-most-beautiful-item-for-each-query
2188-minimized-maximum-of-products-distributed-to-any-store
2255-minimum-swaps-to-group-all-1s-together-ii
2306-create-binary-tree-from-descriptions
2343-count-unguarded-cells-in-the-grid
2356-largest-combination-with-bitwise-and-greater-than-zero
2375-minimum-obstacle-removal-to-reach-corner
2411-spiral-matrix-iv
2432-number-of-zero-filled-subarrays
2448-count-number-of-bad-pairs
2488-divide-intervals-into-minimum-number-of-groups
2494-sum-of-prefix-scores-of-strings
2502-sort-the-people
2503-longest-subarray-with-maximum-bitwise-and
2533-bitwise-xor-of-all-pairings
2545-height-of-binary-tree-after-subtree-removal-queries
2552-maximum-sum-of-distinct-subarrays-with-length-k
2554-minimum-total-distance-traveled
2581-divide-players-into-teams-of-equal-skill
2586-longest-square-streak-in-an-array
2616-maximal-score-after-applying-k-operations
2640-maximum-number-of-integers-to-choose-from-a-range-i
2685-first-completely-painted-row-or-column
2692-take-gifts-from-the-richest-pile
2695-find-score-of-an-array-after-marking-all-elements
2699-count-the-number-of-fair-pairs
2711-minimum-time-to-visit-a-cell-in-a-grid
2716-prime-subtraction-operation
2727-number-of-senior-citizens
2755-extra-characters-in-a-string
2792-neighboring-bitwise-xor
2794-maximum-number-of-moves-in-a-grid
2846-robot-collisions
2891-maximum-beauty-of-an-array-after-applying-operation
3005-count-elements-with-maximum-frequency	Easy
3235-minimum-cost-to-convert-string-i
3291-find-if-array-can-be-sorted
3329-find-the-length-of-the-longest-common-prefix
3332-minimum-operations-to-exceed-threshold-value-ii
3380-shortest-subarray-with-or-at-least-k-ii
3427-special-array-ii
3501-delete-nodes-from-linked-list-present-in-array
3517-shortest-distance-after-road-addition-queries-i
3522-find-the-power-of-k-size-subarrays-i

Binary Search

Problem Name	Difficulty
0033-search-in-rotated-sorted-array	Medium
0035-search-insert-position
0153-find-minimum-in-rotated-sorted-array	Medium
0209-minimum-size-subarray-sum
0268-missing-number	Easy
0287-find-the-duplicate-number	Medium
0350-intersection-of-two-arrays-ii
0719-find-k-th-smallest-pair-distance
0729-my-calendar-i
0731-my-calendar-ii
0892-shortest-subarray-with-sum-at-least-k
1468-check-if-n-and-its-double-exist
1615-range-sum-of-sorted-subarray-sums
1631-path-with-minimum-effort	Medium
1679-shortest-subarray-to-be-removed-to-make-array-sorted
1766-minimum-number-of-removals-to-make-mountain-array
1886-minimum-limit-of-balls-in-a-bag
2006-find-the-student-that-will-replace-the-chalk
2164-two-best-non-overlapping-events
2179-most-beautiful-item-for-each-query
2188-minimized-maximum-of-products-distributed-to-any-store
2586-longest-square-streak-in-an-array
2640-maximum-number-of-integers-to-choose-from-a-range-i
2699-count-the-number-of-fair-pairs
2716-prime-subtraction-operation
2891-maximum-beauty-of-an-array-after-applying-operation
3267-find-longest-special-substring-that-occurs-thrice-i
3427-special-array-ii

Simulation

Problem Name	Difficulty
0054-spiral-matrix	Medium
0592-fraction-addition-and-subtraction
0735-asteroid-collision
0906-walking-robot-simulation
0921-spiral-matrix-iii
0987-reveal-cards-in-increasing-order
1642-water-bottles
1803-average-waiting-time
1951-find-the-winner-of-the-circular-game
2006-find-the-student-that-will-replace-the-chalk
2021-remove-all-occurrences-of-a-substring
2076-sum-of-digits-of-string-after-convert
2155-find-missing-observations
2299-merge-nodes-in-between-zeros
2343-count-unguarded-cells-in-the-grid
2408-number-of-people-aware-of-a-secret
2411-spiral-matrix-iv
2692-take-gifts-from-the-richest-pile
2695-find-score-of-an-array-after-marking-all-elements
2800-minimum-string-length-after-removing-substrings
2846-robot-collisions
3332-minimum-operations-to-exceed-threshold-value-ii
3447-clear-digits

String

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters
0071-simplify-path
0126-word-ladder-ii	Hard
0127-word-ladder	Hard
0214-shortest-palindrome
0241-different-ways-to-add-parentheses
0273-integer-to-english-words
0316-remove-duplicate-letters
0344-reverse-string
0394-decode-string
0516-longest-palindromic-subsequence
0539-minimum-time-difference
0564-find-the-closest-palindrome
0567-permutation-in-string
0592-fraction-addition-and-subtraction
0664-strange-printer
0721-accounts-merge	Medium
0726-number-of-atoms
0812-rotate-string
0920-uncommon-words-from-two-sentences
0957-minimum-add-to-make-parentheses-valid
1045-check-if-word-is-valid-after-substitutions
1128-remove-all-adjacent-duplicates-in-string
1160-letter-tile-possibilities
1197-parsing-a-boolean-expression
1250-longest-common-subsequence
1298-reverse-substrings-between-each-pair-of-parentheses
1302-delete-characters-to-make-fancy-string
1304-longest-happy-string
1350-remove-sub-folders-from-the-filesystem
1473-find-the-longest-substring-containing-vowels-in-even-counts
1566-check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence
1715-split-a-string-into-the-max-number-of-unique-substrings
1720-crawler-log-folder
1756-minimum-deletions-to-make-string-balanced
1786-count-the-number-of-consistent-strings
1818-maximum-score-from-removing-substrings
1923-sentence-similarity-iii
2021-remove-all-occurrences-of-a-substring
2076-sum-of-digits-of-string-after-convert
2095-minimum-number-of-swaps-to-make-the-string-balanced
2163-kth-distinct-string-in-an-array
2217-step-by-step-directions-from-a-binary-tree-node-to-another
2414-move-pieces-to-obtain-a-string
2494-sum-of-prefix-scores-of-strings
2502-sort-the-people
2580-circular-sentence
2599-take-k-of-each-character-from-left-and-right
2727-number-of-senior-citizens
2755-extra-characters-in-a-string
2800-minimum-string-length-after-removing-substrings
3018-make-string-a-subsequence-using-cyclic-increments
3174-minimum-number-of-changes-to-make-binary-string-beautiful
3195-separate-black-and-white-balls
3235-minimum-cost-to-convert-string-i
3267-find-longest-special-substring-that-occurs-thrice-i
3276-minimum-number-of-pushes-to-type-word-ii
3329-find-the-length-of-the-longest-common-prefix
3447-clear-digits
3451-string-compression-iii

Math

Problem Name	Difficulty
0048-rotate-image	Medium
0189-rotate-array	Medium
0241-different-ways-to-add-parentheses
0264-ugly-number-ii
0268-missing-number	Easy
0273-integer-to-english-words
0539-minimum-time-difference
0564-find-the-closest-palindrome
0592-fraction-addition-and-subtraction
0650-2-keys-keyboard
0670-maximum-swap
0870-magic-squares-in-grid
0909-stone-game
1240-stone-game-ii
1477-product-of-the-last-k-numbers
1642-water-bottles
1951-find-the-winner-of-the-circular-game
2139-minimum-moves-to-reach-target-score	Medium
2155-find-missing-observations
2432-number-of-zero-filled-subarrays
2448-count-number-of-bad-pairs
2716-prime-subtraction-operation
2802-find-the-punishment-number-of-an-integer
2903-insert-greatest-common-divisors-in-linked-list

Stack

Problem Name	Difficulty
0071-simplify-path
0084-largest-rectangle-in-histogram
0094-binary-tree-inorder-traversal
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0155-min-stack
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0316-remove-duplicate-letters
0394-decode-string
0726-number-of-atoms
0735-asteroid-collision
0739-daily-temperatures
0776-n-ary-tree-postorder-traversal
0883-car-fleet
0957-minimum-add-to-make-parentheses-valid
1002-maximum-width-ramp
1045-check-if-word-is-valid-after-substitutions
1050-construct-binary-search-tree-from-preorder-traversal
1128-remove-all-adjacent-duplicates-in-string
1197-parsing-a-boolean-expression
1298-reverse-substrings-between-each-pair-of-parentheses
1497-design-a-stack-with-increment-operation
1679-shortest-subarray-to-be-removed-to-make-array-sorted
1720-crawler-log-folder
1756-minimum-deletions-to-make-string-balanced
1818-maximum-score-from-removing-substrings
2021-remove-all-occurrences-of-a-substring
2095-minimum-number-of-swaps-to-make-the-string-balanced
2800-minimum-string-length-after-removing-substrings
2846-robot-collisions
3447-clear-digits

Design

Problem Name	Difficulty
0155-min-stack
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0432-all-oone-data-structure
0729-my-calendar-i
0731-my-calendar-ii
0789-kth-largest-element-in-a-stream
0859-design-circular-deque
0969-number-of-recent-calls
1477-product-of-the-last-k-numbers
1497-design-a-stack-with-increment-operation
2434-design-a-number-container-system

Monotonic Stack

Problem Name	Difficulty
0084-largest-rectangle-in-histogram
0316-remove-duplicate-letters
0739-daily-temperatures
0883-car-fleet
1002-maximum-width-ramp
1050-construct-binary-search-tree-from-preorder-traversal
1679-shortest-subarray-to-be-removed-to-make-array-sorted

Queue

Problem Name	Difficulty
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0239-sliding-window-maximum
0859-design-circular-deque
0892-shortest-subarray-with-sum-at-least-k
0969-number-of-recent-calls
0987-reveal-cards-in-increasing-order
1951-find-the-winner-of-the-circular-game
2408-number-of-people-aware-of-a-secret

Sliding Window

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters
0209-minimum-size-subarray-sum
0239-sliding-window-maximum
0567-permutation-in-string
0643-maximum-average-subarray-i	Easy
0892-shortest-subarray-with-sum-at-least-k
1755-defuse-the-bomb
2255-minimum-swaps-to-group-all-1s-together-ii
2552-maximum-sum-of-distinct-subarrays-with-length-k
2599-take-k-of-each-character-from-left-and-right
2891-maximum-beauty-of-an-array-after-applying-operation
3267-find-longest-special-substring-that-occurs-thrice-i
3380-shortest-subarray-with-or-at-least-k-ii
3522-find-the-power-of-k-size-subarrays-i

Monotonic Queue

Problem Name	Difficulty
0239-sliding-window-maximum
0892-shortest-subarray-with-sum-at-least-k

Data Stream

Problem Name	Difficulty
0789-kth-largest-element-in-a-stream
0969-number-of-recent-calls
1477-product-of-the-last-k-numbers

Dynamic Programming

Problem Name	Difficulty
0053-maximum-subarray
0064-minimum-path-sum	Medium
0241-different-ways-to-add-parentheses
0264-ugly-number-ii
0516-longest-palindromic-subsequence
0650-2-keys-keyboard
0664-strange-printer
0909-stone-game
1025-minimum-cost-for-tickets
1196-filling-bookcase-shelves
1240-stone-game-ii
1250-longest-common-subsequence
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance	Medium
1402-count-square-submatrices-with-all-ones
1456-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1511-count-number-of-teams
1756-minimum-deletions-to-make-string-balanced
1766-minimum-number-of-removals-to-make-mountain-array
2067-maximum-number-of-points-with-cost
2164-two-best-non-overlapping-events
2408-number-of-people-aware-of-a-secret
2554-minimum-total-distance-traveled
2586-longest-square-streak-in-an-array
2755-extra-characters-in-a-string
2794-maximum-number-of-moves-in-a-grid

Tree

Problem Name	Difficulty
0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0110-balanced-binary-tree
0112-path-sum
0113-path-sum-ii
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0437-path-sum-iii
0543-diameter-of-binary-tree
0652-find-duplicate-subtrees
0653-two-sum-iv-input-is-a-bst
0776-n-ary-tree-postorder-traversal
0789-kth-largest-element-in-a-stream
0975-range-sum-of-bst
0988-flip-equivalent-binary-trees
1029-vertical-order-traversal-of-a-binary-tree
1050-construct-binary-search-tree-from-preorder-traversal
1207-delete-nodes-and-return-forest
1285-balance-a-binary-search-tree
1484-linked-list-in-binary-tree
1653-number-of-good-leaf-nodes-pairs
2217-step-by-step-directions-from-a-binary-tree-node-to-another
2306-create-binary-tree-from-descriptions
2545-height-of-binary-tree-after-subtree-removal-queries
2646-kth-largest-sum-in-a-binary-tree
2677-cousins-in-binary-tree-ii

Binary Tree

Problem Name	Difficulty
0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0110-balanced-binary-tree
0112-path-sum
0113-path-sum-ii
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0437-path-sum-iii
0543-diameter-of-binary-tree
0652-find-duplicate-subtrees
0653-two-sum-iv-input-is-a-bst
0789-kth-largest-element-in-a-stream
0975-range-sum-of-bst
0988-flip-equivalent-binary-trees
1029-vertical-order-traversal-of-a-binary-tree
1050-construct-binary-search-tree-from-preorder-traversal
1207-delete-nodes-and-return-forest
1285-balance-a-binary-search-tree
1484-linked-list-in-binary-tree
1653-number-of-good-leaf-nodes-pairs
2217-step-by-step-directions-from-a-binary-tree-node-to-another
2306-create-binary-tree-from-descriptions
2545-height-of-binary-tree-after-subtree-removal-queries
2646-kth-largest-sum-in-a-binary-tree
2677-cousins-in-binary-tree-ii

Depth-First Search

Problem Name	Difficulty
0094-binary-tree-inorder-traversal
0098-validate-binary-search-tree
0104-maximum-depth-of-binary-tree
0110-balanced-binary-tree
0112-path-sum
0113-path-sum-ii
0144-binary-tree-preorder-traversal
0145-binary-tree-postorder-traversal
0200-number-of-islands	Medium
0207-course-schedule	Medium
0210-course-schedule-ii	Medium
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0236-lowest-common-ancestor-of-a-binary-tree
0310-minimum-height-trees	Medium
0386-lexicographical-numbers
0417-pacific-atlantic-water-flow	Medium
0437-path-sum-iii
0543-diameter-of-binary-tree
0547-number-of-provinces	Medium
0652-find-duplicate-subtrees
0653-two-sum-iv-input-is-a-bst
0684-redundant-connection	Medium
0721-accounts-merge	Medium
0733-flood-fill	Easy
0743-network-delay-time	Medium
0776-n-ary-tree-postorder-traversal
0785-is-graph-bipartite	Medium
0797-all-paths-from-source-to-target	Medium
0802-find-eventual-safe-states	Medium
0820-find-eventual-safe-states
0841-keys-and-rooms	Medium
0975-range-sum-of-bst
0984-most-stones-removed-with-same-row-or-column
0988-flip-equivalent-binary-trees
0999-regions-cut-by-slashes
1029-vertical-order-traversal-of-a-binary-tree
1192-critical-connections-in-a-network	Hard
1207-delete-nodes-and-return-forest
1285-balance-a-binary-search-tree
1306-jump-game-iii	Medium
1319-number-of-operations-to-make-network-connected	Medium
1350-remove-sub-folders-from-the-filesystem
1396-count-servers-that-communicate
1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero	Medium
1484-linked-list-in-binary-tree
1631-path-with-minimum-effort	Medium
1653-number-of-good-leaf-nodes-pairs
1691-minimum-number-of-days-to-disconnect-island
2035-count-sub-islands
2201-valid-arrangement-of-pairs
2217-step-by-step-directions-from-a-binary-tree-node-to-another
2360-longest-cycle-in-a-graph	Hard
2545-height-of-binary-tree-after-subtree-removal-queries
2677-cousins-in-binary-tree-ii

Breadth-First Search

Problem Name	Difficulty
0103-binary-tree-zigzag-level-order-traversal
0104-maximum-depth-of-binary-tree
0112-path-sum
0126-word-ladder-ii	Hard
0127-word-ladder	Hard
0200-number-of-islands	Medium
0207-course-schedule	Medium
0210-course-schedule-ii	Medium
0310-minimum-height-trees	Medium
0407-trapping-rain-water-ii
0417-pacific-atlantic-water-flow	Medium
0547-number-of-provinces	Medium
0653-two-sum-iv-input-is-a-bst
0684-redundant-connection	Medium
0721-accounts-merge	Medium
0733-flood-fill	Easy
0743-network-delay-time	Medium
0785-is-graph-bipartite	Medium
0787-sliding-puzzle
0797-all-paths-from-source-to-target	Medium
0802-find-eventual-safe-states	Medium
0820-find-eventual-safe-states
0841-keys-and-rooms	Medium
0994-rotting-oranges	Medium
0999-regions-cut-by-slashes
1029-vertical-order-traversal-of-a-binary-tree
1306-jump-game-iii	Medium
1319-number-of-operations-to-make-network-connected	Medium
1396-count-servers-that-communicate
1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero	Medium
1484-linked-list-in-binary-tree
1485-minimum-cost-to-make-at-least-one-valid-path-in-a-grid
1631-path-with-minimum-effort	Medium
1691-minimum-number-of-days-to-disconnect-island
1876-map-of-highest-peak
2035-count-sub-islands
2171-second-minimum-time-to-reach-destination
2360-longest-cycle-in-a-graph	Hard
2375-minimum-obstacle-removal-to-reach-corner
2545-height-of-binary-tree-after-subtree-removal-queries
2646-kth-largest-sum-in-a-binary-tree
2677-cousins-in-binary-tree-ii
2711-minimum-time-to-visit-a-cell-in-a-grid
3517-shortest-distance-after-road-addition-queries-i

Backtracking

Problem Name	Difficulty
0040-combination-sum-ii
0113-path-sum-ii
0126-word-ladder-ii	Hard
0797-all-paths-from-source-to-target	Medium
1160-letter-tile-possibilities
1715-split-a-string-into-the-max-number-of-unique-substrings
1819-construct-the-lexicographically-largest-valid-sequence
2170-count-number-of-maximum-bitwise-or-subsets
2802-find-the-punishment-number-of-an-integer

Matrix

Problem Name	Difficulty
0048-rotate-image	Medium
0054-spiral-matrix	Medium
0064-minimum-path-sum	Medium
0073-set-matrix-zeroes	Medium
0200-number-of-islands	Medium
0407-trapping-rain-water-ii
0417-pacific-atlantic-water-flow	Medium
0733-flood-fill	Easy
0787-sliding-puzzle
0870-magic-squares-in-grid
0921-spiral-matrix-iii
0994-rotting-oranges	Medium
0999-regions-cut-by-slashes
1147-flip-columns-for-maximum-number-of-equal-rows
1396-count-servers-that-communicate
1402-count-square-submatrices-with-all-ones
1485-minimum-cost-to-make-at-least-one-valid-path-in-a-grid
1496-lucky-numbers-in-a-matrix
1631-path-with-minimum-effort	Medium
1691-minimum-number-of-days-to-disconnect-island
1876-map-of-highest-peak
1972-rotating-the-box
2035-count-sub-islands
2089-maximum-matrix-sum
2145-grid-game
2343-count-unguarded-cells-in-the-grid
2375-minimum-obstacle-removal-to-reach-corner
2411-spiral-matrix-iv
2685-first-completely-painted-row-or-column
2711-minimum-time-to-visit-a-cell-in-a-grid
2794-maximum-number-of-moves-in-a-grid

Bucket Sort

Problem Name	Difficulty
0347-top-k-frequent-elements	Medium
0948-sort-an-array

Radix Sort

Problem Name	Difficulty
0948-sort-an-array

Counting Sort

Problem Name	Difficulty
0347-top-k-frequent-elements	Medium
0920-uncommon-words-from-two-sentences
0948-sort-an-array
1160-letter-tile-possibilities
1396-count-servers-that-communicate
1620-check-if-array-pairs-are-divisible-by-k
1786-count-the-number-of-consistent-strings
2163-kth-distinct-string-in-an-array
2356-largest-combination-with-bitwise-and-greater-than-zero
2448-count-number-of-bad-pairs
2494-sum-of-prefix-scores-of-strings
3005-count-elements-with-maximum-frequency	Easy
3267-find-longest-special-substring-that-occurs-thrice-i
3276-minimum-number-of-pushes-to-type-word-ii

Shortest Path

Problem Name	Difficulty
0743-network-delay-time	Medium
1325-path-with-maximum-probability
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance	Medium
1456-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance
1485-minimum-cost-to-make-at-least-one-valid-path-in-a-grid
2171-second-minimum-time-to-reach-destination
2375-minimum-obstacle-removal-to-reach-corner
2711-minimum-time-to-visit-a-cell-in-a-grid
2803-modify-graph-edge-weights
3235-minimum-cost-to-convert-string-i

Binary Indexed Tree

Problem Name	Difficulty
1511-count-number-of-teams

Binary Search Tree

Problem Name	Difficulty
0098-validate-binary-search-tree
0230-kth-smallest-element-in-a-bst
0235-lowest-common-ancestor-of-a-binary-search-tree
0653-two-sum-iv-input-is-a-bst
0789-kth-largest-element-in-a-stream
0975-range-sum-of-bst
1050-construct-binary-search-tree-from-preorder-traversal
1285-balance-a-binary-search-tree

Union Find

Problem Name	Difficulty
0984-most-stones-removed-with-same-row-or-column
0999-regions-cut-by-slashes
1396-count-servers-that-communicate
2035-count-sub-islands

Strongly Connected Component

Problem Name	Difficulty
1691-minimum-number-of-days-to-disconnect-island

Prefix Sum

Problem Name	Difficulty
0209-minimum-size-subarray-sum
0238-product-of-array-except-self	Medium
0525-contiguous-array	Medium
0560-subarray-sum-equals-k	Medium
0724-find-pivot-index	Easy
0731-my-calendar-ii
0892-shortest-subarray-with-sum-at-least-k
1240-stone-game-ii
1435-xor-queries-of-a-subarray
1473-find-the-longest-substring-containing-vowels-in-even-counts
1477-product-of-the-last-k-numbers
1694-make-sum-divisible-by-p
1940-maximum-xor-for-each-query
2006-find-the-student-that-will-replace-the-chalk
2145-grid-game
2488-divide-intervals-into-minimum-number-of-groups
3427-special-array-ii

Game Theory

Problem Name	Difficulty
0909-stone-game
1240-stone-game-ii

Bit Manipulation

Problem Name	Difficulty
0268-missing-number	Easy
0287-find-the-duplicate-number	Medium
0476-number-complement
1054-complement-of-base-10-integer
1435-xor-queries-of-a-subarray
1473-find-the-longest-substring-containing-vowels-in-even-counts
1786-count-the-number-of-consistent-strings
1940-maximum-xor-for-each-query
2170-count-number-of-maximum-bitwise-or-subsets
2323-minimum-bit-flips-to-convert-number
2356-largest-combination-with-bitwise-and-greater-than-zero
2503-longest-subarray-with-maximum-bitwise-and
2533-bitwise-xor-of-all-pairings
2792-neighboring-bitwise-xor
3291-find-if-array-can-be-sorted
3380-shortest-subarray-with-or-at-least-k-ii
3394-minimum-array-end

Number Theory

Problem Name	Difficulty
2716-prime-subtraction-operation
2903-insert-greatest-common-divisors-in-linked-list

Brainteaser

Problem Name	Difficulty
2503-longest-subarray-with-maximum-bitwise-and
2533-bitwise-xor-of-all-pairings

Memoization

Problem Name	Difficulty
0241-different-ways-to-add-parentheses

Rolling Hash

Problem Name	Difficulty
0214-shortest-palindrome

String Matching

Problem Name	Difficulty
0214-shortest-palindrome
0812-rotate-string
1566-check-if-a-word-occurs-as-a-prefix-of-any-word-in-a-sentence

Hash Function

Problem Name	Difficulty
0214-shortest-palindrome

Trie

Problem Name	Difficulty
0386-lexicographical-numbers
0440-k-th-smallest-in-lexicographical-order
1350-remove-sub-folders-from-the-filesystem
2494-sum-of-prefix-scores-of-strings
2755-extra-characters-in-a-string
3329-find-the-length-of-the-longest-common-prefix

Segment Tree

Problem Name	Difficulty
0729-my-calendar-i
0731-my-calendar-ii

Ordered Set

Problem Name	Difficulty
0729-my-calendar-i
0731-my-calendar-ii
2434-design-a-number-container-system

Doubly-Linked List

Problem Name	Difficulty
0432-all-oone-data-structure

Enumeration

Problem Name	Difficulty
2170-count-number-of-maximum-bitwise-or-subsets

Eulerian Circuit

Problem Name	Difficulty
2201-valid-arrangement-of-pairs

Topological Sort

Problem Name	Difficulty
0207-course-schedule	Medium
0210-course-schedule-ii	Medium
0310-minimum-height-trees	Medium
0802-find-eventual-safe-states	Medium
0820-find-eventual-safe-states
2360-longest-cycle-in-a-graph	Hard

Graph Theory

Problem Name	Difficulty
0207-course-schedule	Medium
0210-course-schedule-ii	Medium
0310-minimum-height-trees	Medium
0547-number-of-provinces	Medium
0684-redundant-connection	Medium
0743-network-delay-time	Medium
0785-is-graph-bipartite	Medium
0797-all-paths-from-source-to-target	Medium
0802-find-eventual-safe-states	Medium
0841-keys-and-rooms	Medium
0997-find-the-town-judge	Easy
1192-critical-connections-in-a-network	Hard
1319-number-of-operations-to-make-network-connected	Medium
1334-find-the-city-with-the-smallest-number-of-neighbors-at-a-threshold-distance	Medium
1466-reorder-routes-to-make-all-paths-lead-to-the-city-zero	Medium
2360-longest-cycle-in-a-graph	Hard

Union-Find

Problem Name	Difficulty
0200-number-of-islands	Medium
0547-number-of-provinces	Medium
0684-redundant-connection	Medium
0721-accounts-merge	Medium
0785-is-graph-bipartite	Medium
1319-number-of-operations-to-make-network-connected	Medium
1631-path-with-minimum-effort	Medium

Biconnected Component

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

Quickselect

Problem Name	Difficulty
0215-kth-largest-element-in-an-array	Medium
0347-top-k-frequent-elements	Medium