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LeetCode Topics

LeetCode Topics👇🏻

Problem Name	Difficulty

Array

Problem Name	Difficulty
0001-two-sum
0004-median-of-two-sorted-arrays
0026-remove-duplicates-from-sorted-array
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0064-minimum-path-sum
0079-word-search
0081-search-in-rotated-sorted-array-ii
0084-largest-rectangle-in-histogram
0085-maximal-rectangle
0088-merge-sorted-array
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0189-rotate-array
0209-minimum-size-subarray-sum	Medium
0215-kth-largest-element-in-an-array
0221-maximal-square
0239-sliding-window-maximum
0274-h-index
0275-h-index-ii
0289-game-of-life
0410-split-array-largest-sum
0413-arithmetic-slices	Medium
0442-find-all-duplicates-in-an-array
0496-next-greater-element-i
0503-next-greater-element-ii
0540-single-element-in-a-sorted-array
0561-array-partition
0594-longest-harmonious-subsequence	Easy
0641-design-circular-deque
0735-asteroid-collision
0875-koko-eating-bananas
0907-sum-of-subarray-minimums
0950-reveal-cards-in-increasing-order
1011-capacity-to-ship-packages-within-d-days
1019-next-greater-node-in-linked-list
1046-last-stone-weight
1051-height-checker
1122-relative-sort-array
1283-find-the-smallest-divisor-given-a-threshold
1365-how-many-numbers-are-smaller-than-the-current-number
1482-minimum-number-of-days-to-make-m-bouquets
1539-kth-missing-positive-number
1670-design-front-middle-back-queue
1700-number-of-students-unable-to-eat-lunch
1901-find-a-peak-element-ii
1929-concatenation-of-array
2037-minimum-number-of-moves-to-seat-everyone
2104-sum-of-subarray-ranges
3217-delete-nodes-from-linked-list-present-in-array
3364-minimum-positive-sum-subarray	Easy

Hash Table

Problem Name	Difficulty
0001-two-sum
0003-longest-substring-without-repeating-characters	Medium
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0141-linked-list-cycle
0142-linked-list-cycle-ii
0160-intersection-of-two-linked-lists
0187-repeated-dna-sequences	Medium
0242-valid-anagram
0290-word-pattern
0383-ransom-note
0387-first-unique-character-in-a-string
0395-longest-substring-with-at-least-k-repeating-characters	Medium
0442-find-all-duplicates-in-an-array
0496-next-greater-element-i
0594-longest-harmonious-subsequence	Easy
1122-relative-sort-array
1365-how-many-numbers-are-smaller-than-the-current-number
3217-delete-nodes-from-linked-list-present-in-array

Math

Problem Name	Difficulty
0002-add-two-numbers
0009-palindrome-number
0069-sqrtx
0096-unique-binary-search-trees	Medium
0189-rotate-array
0224-basic-calculator
0227-basic-calculator-ii
0367-valid-perfect-square
1013-fibonacci-number

Greedy

Problem Name	Difficulty
0316-remove-duplicate-letters
0402-remove-k-digits
0410-split-array-largest-sum
0561-array-partition
2037-minimum-number-of-moves-to-seat-everyone
3474-lexicographically-smallest-generated-string

Sorting

Problem Name	Difficulty
0088-merge-sorted-array
0147-insertion-sort-list
0215-kth-largest-element-in-an-array
0242-valid-anagram
0274-h-index
0442-find-all-duplicates-in-an-array
0561-array-partition
0594-longest-harmonious-subsequence	Easy
0950-reveal-cards-in-increasing-order
1051-height-checker
1122-relative-sort-array
1365-how-many-numbers-are-smaller-than-the-current-number
2037-minimum-number-of-moves-to-seat-everyone
3517-smallest-palindromic-rearrangement-i

Counting Sort

Problem Name	Difficulty
0274-h-index
0383-ransom-note
0387-first-unique-character-in-a-string
0561-array-partition
0594-longest-harmonious-subsequence	Easy
1051-height-checker
1122-relative-sort-array
1365-how-many-numbers-are-smaller-than-the-current-number
2037-minimum-number-of-moves-to-seat-everyone
3517-smallest-palindromic-rearrangement-i

Binary Search

Problem Name	Difficulty
0004-median-of-two-sorted-arrays
0033-search-in-rotated-sorted-array
0034-find-first-and-last-position-of-element-in-sorted-array
0035-search-insert-position
0069-sqrtx
0081-search-in-rotated-sorted-array-ii
0153-find-minimum-in-rotated-sorted-array
0162-find-peak-element
0167-two-sum-ii-input-array-is-sorted
0209-minimum-size-subarray-sum	Medium
0275-h-index-ii
0278-first-bad-version
0367-valid-perfect-square
0410-split-array-largest-sum
0540-single-element-in-a-sorted-array
0875-koko-eating-bananas
1011-capacity-to-ship-packages-within-d-days
1283-find-the-smallest-divisor-given-a-threshold
1482-minimum-number-of-days-to-make-m-bouquets
1539-kth-missing-positive-number
1901-find-a-peak-element-ii

Divide and Conquer

Problem Name	Difficulty
0004-median-of-two-sorted-arrays
0023-merge-k-sorted-lists
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0109-convert-sorted-list-to-binary-search-tree
0215-kth-largest-element-in-an-array
0395-longest-substring-with-at-least-k-repeating-characters	Medium

Two Pointers

Problem Name	Difficulty
0019-remove-nth-node-from-end-of-list
0026-remove-duplicates-from-sorted-array
0061-rotate-list
0082-remove-duplicates-from-sorted-list-ii
0086-partition-list
0088-merge-sorted-array
0141-linked-list-cycle
0142-linked-list-cycle-ii
0143-reorder-list
0160-intersection-of-two-linked-lists
0167-two-sum-ii-input-array-is-sorted
0189-rotate-array
0234-palindrome-linked-list
0876-middle-of-the-linked-list
1721-swapping-nodes-in-a-linked-list
2095-delete-the-middle-node-of-a-linked-list

Dynamic Programming

Problem Name	Difficulty
0064-minimum-path-sum
0085-maximal-rectangle
0096-unique-binary-search-trees	Medium
0221-maximal-square
0410-split-array-largest-sum
0413-arithmetic-slices	Medium
0907-sum-of-subarray-minimums
1013-fibonacci-number

Recursion

Problem Name	Difficulty
0002-add-two-numbers
0024-swap-nodes-in-pairs
0143-reorder-list
0203-remove-linked-list-elements
0206-reverse-linked-list
0224-basic-calculator
0234-palindrome-linked-list
1013-fibonacci-number

Memoization

Problem Name	Difficulty
1013-fibonacci-number

Matrix

Problem Name	Difficulty
0064-minimum-path-sum
0079-word-search
0085-maximal-rectangle
0221-maximal-square
0289-game-of-life
1901-find-a-peak-element-ii

String

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0020-valid-parentheses
0071-simplify-path
0079-word-search
0187-repeated-dna-sequences	Medium
0224-basic-calculator
0227-basic-calculator-ii
0242-valid-anagram
0290-word-pattern
0316-remove-duplicate-letters
0383-ransom-note
0387-first-unique-character-in-a-string
0395-longest-substring-with-at-least-k-repeating-characters	Medium
0402-remove-k-digits
0657-robot-return-to-origin
1047-remove-all-adjacent-duplicates-in-string
3474-lexicographically-smallest-generated-string
3517-smallest-palindromic-rearrangement-i

Stack

Problem Name	Difficulty
0020-valid-parentheses
0071-simplify-path
0084-largest-rectangle-in-histogram
0085-maximal-rectangle
0094-binary-tree-inorder-traversal	Easy
0143-reorder-list
0144-binary-tree-preorder-traversal	Easy
0145-binary-tree-postorder-traversal	Easy
0155-min-stack
0224-basic-calculator
0225-implement-stack-using-queues
0227-basic-calculator-ii
0232-implement-queue-using-stacks
0234-palindrome-linked-list
0316-remove-duplicate-letters
0402-remove-k-digits
0496-next-greater-element-i
0503-next-greater-element-ii
0735-asteroid-collision
0897-increasing-order-search-tree
0901-online-stock-span
0907-sum-of-subarray-minimums
1019-next-greater-node-in-linked-list
1047-remove-all-adjacent-duplicates-in-string
1700-number-of-students-unable-to-eat-lunch
2104-sum-of-subarray-ranges

Interactive

Problem Name	Difficulty
0278-first-bad-version

Monotonic Stack

Problem Name	Difficulty
0084-largest-rectangle-in-histogram
0085-maximal-rectangle
0316-remove-duplicate-letters
0402-remove-k-digits
0496-next-greater-element-i
0503-next-greater-element-ii
0901-online-stock-span
0907-sum-of-subarray-minimums
1019-next-greater-node-in-linked-list
2104-sum-of-subarray-ranges

Simulation

Problem Name	Difficulty
0289-game-of-life
0657-robot-return-to-origin
0735-asteroid-collision
0950-reveal-cards-in-increasing-order
1700-number-of-students-unable-to-eat-lunch
1929-concatenation-of-array

Linked List

Problem Name	Difficulty
0002-add-two-numbers
0019-remove-nth-node-from-end-of-list
0023-merge-k-sorted-lists
0024-swap-nodes-in-pairs
0061-rotate-list
0082-remove-duplicates-from-sorted-list-ii
0083-remove-duplicates-from-sorted-list
0086-partition-list
0092-reverse-linked-list-ii
0109-convert-sorted-list-to-binary-search-tree
0141-linked-list-cycle
0142-linked-list-cycle-ii
0143-reorder-list
0147-insertion-sort-list
0160-intersection-of-two-linked-lists
0203-remove-linked-list-elements
0206-reverse-linked-list
0234-palindrome-linked-list
0237-delete-node-in-a-linked-list
0328-odd-even-linked-list
0641-design-circular-deque
0876-middle-of-the-linked-list
1019-next-greater-node-in-linked-list
1670-design-front-middle-back-queue
1721-swapping-nodes-in-a-linked-list
2095-delete-the-middle-node-of-a-linked-list
3217-delete-nodes-from-linked-list-present-in-array

Prefix Sum

Problem Name	Difficulty
0209-minimum-size-subarray-sum	Medium
0410-split-array-largest-sum
3364-minimum-positive-sum-subarray	Easy

Heap (Priority Queue)

Problem Name	Difficulty
0023-merge-k-sorted-lists
0215-kth-largest-element-in-an-array
0239-sliding-window-maximum
1046-last-stone-weight

Merge Sort

Problem Name	Difficulty
0023-merge-k-sorted-lists

Tree

Problem Name	Difficulty
0094-binary-tree-inorder-traversal	Easy
0096-unique-binary-search-trees	Medium
0100-same-tree	Easy
0101-symmetric-tree	Easy
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree	Easy
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree	Easy
0112-path-sum	Easy
0113-path-sum-ii	Medium
0144-binary-tree-preorder-traversal	Easy
0145-binary-tree-postorder-traversal	Easy
0897-increasing-order-search-tree

Binary Search Tree

Problem Name	Difficulty
0096-unique-binary-search-trees	Medium
0109-convert-sorted-list-to-binary-search-tree
0897-increasing-order-search-tree

Binary Tree

Problem Name	Difficulty
0094-binary-tree-inorder-traversal	Easy
0096-unique-binary-search-trees	Medium
0100-same-tree	Easy
0101-symmetric-tree	Easy
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree	Easy
0105-construct-binary-tree-from-preorder-and-inorder-traversal
0109-convert-sorted-list-to-binary-search-tree
0110-balanced-binary-tree	Easy
0112-path-sum	Easy
0113-path-sum-ii	Medium
0144-binary-tree-preorder-traversal	Easy
0145-binary-tree-postorder-traversal	Easy
0897-increasing-order-search-tree

Design

Problem Name	Difficulty
0155-min-stack
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0641-design-circular-deque
0901-online-stock-span
0933-number-of-recent-calls
1670-design-front-middle-back-queue

Queue

Problem Name	Difficulty
0225-implement-stack-using-queues
0232-implement-queue-using-stacks
0239-sliding-window-maximum
0387-first-unique-character-in-a-string
0641-design-circular-deque
0933-number-of-recent-calls
0950-reveal-cards-in-increasing-order
1670-design-front-middle-back-queue
1700-number-of-students-unable-to-eat-lunch

Data Stream

Problem Name	Difficulty
0901-online-stock-span
0933-number-of-recent-calls
1670-design-front-middle-back-queue

Depth-First Search

Problem Name	Difficulty
0079-word-search
0094-binary-tree-inorder-traversal	Easy
0100-same-tree	Easy
0101-symmetric-tree	Easy
0104-maximum-depth-of-binary-tree	Easy
0110-balanced-binary-tree	Easy
0112-path-sum	Easy
0113-path-sum-ii	Medium
0144-binary-tree-preorder-traversal	Easy
0145-binary-tree-postorder-traversal	Easy
0897-increasing-order-search-tree

String Matching

Problem Name	Difficulty
3474-lexicographically-smallest-generated-string

Doubly-Linked List

Problem Name	Difficulty
1670-design-front-middle-back-queue

Sliding Window

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0187-repeated-dna-sequences	Medium
0209-minimum-size-subarray-sum	Medium
0239-sliding-window-maximum
0395-longest-substring-with-at-least-k-repeating-characters	Medium
0413-arithmetic-slices	Medium
0594-longest-harmonious-subsequence	Easy
3364-minimum-positive-sum-subarray	Easy

Monotonic Queue

Problem Name	Difficulty
0239-sliding-window-maximum

Quickselect

Problem Name	Difficulty
0215-kth-largest-element-in-an-array

Breadth-First Search

Problem Name	Difficulty
0100-same-tree	Easy
0101-symmetric-tree	Easy
0102-binary-tree-level-order-traversal
0104-maximum-depth-of-binary-tree	Easy
0112-path-sum	Easy

Backtracking

Problem Name	Difficulty
0079-word-search
0113-path-sum-ii	Medium

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
0185-department-top-three-salaries
0196-delete-duplicate-emails
0197-rising-temperature	Easy
0262-trips-and-users	Hard
0511-game-play-analysis-i	Easy
0550-game-play-analysis-iv	Medium
0570-managers-with-at-least-5-direct-reports	Medium
0585-investments-in-2016	Medium
0586-customer-placing-the-largest-number-of-orders
0595-big-countries
0596-classes-with-at-least-5-students	Easy
0602-friend-requests-ii-who-has-the-most-friends	Medium
0607-sales-person	Easy
0608-tree-node	Medium
0626-exchange-seats	Medium
1158-market-analysis-i	Medium

Bit Manipulation

Problem Name	Difficulty
0187-repeated-dna-sequences	Medium

Rolling Hash

Problem Name	Difficulty
0187-repeated-dna-sequences	Medium

Hash Function

Problem Name	Difficulty
0187-repeated-dna-sequences	Medium