LeetCode Topics

Hash Table

Problem Name	Difficulty
0001-two-sum	Easy
0003-longest-substring-without-repeating-characters	Medium
0017-letter-combinations-of-a-phone-number	Medium
0049-group-anagrams	Medium
0076-minimum-window-substring	Hard
0146-lru-cache	Medium
0347-top-k-frequent-elements	Medium
0349-intersection-of-two-arrays	Easy
0380-insert-delete-getrandom-o1	Medium
0424-longest-repeating-character-replacement	Medium
0706-design-hashmap	Easy
0771-jewels-and-stones	Easy
0819-most-common-word	Easy

Linked List

Problem Name	Difficulty
0002-add-two-numbers	Medium
0021-merge-two-sorted-lists	Easy
0023-merge-k-sorted-lists	Hard
0146-lru-cache	Medium
0206-reverse-linked-list	Easy
0234-palindrome-linked-list	Easy
0622-design-circular-queue	Medium
0641-design-circular-deque	Medium
0706-design-hashmap	Easy

Design

Problem Name	Difficulty
0146-lru-cache	Medium
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy
0380-insert-delete-getrandom-o1	Medium
0622-design-circular-queue	Medium
0641-design-circular-deque	Medium
0706-design-hashmap	Easy

Doubly-Linked List

Problem Name	Difficulty
0146-lru-cache	Medium

Array

Problem Name	Difficulty
0001-two-sum	Easy
0004-median-of-two-sorted-arrays	Hard
0011-container-with-most-water	Medium
0015-3sum	Medium
0033-search-in-rotated-sorted-array	Medium
0039-combination-sum	Medium
0042-trapping-rain-water	Hard
0049-group-anagrams	Medium
0121-best-time-to-buy-and-sell-stock	Easy
0122-best-time-to-buy-and-sell-stock-ii	Medium
0167-two-sum-ii-input-array-is-sorted	Medium
0200-number-of-islands	Medium
0215-kth-largest-element-in-an-array	Medium
0238-product-of-array-except-self	Medium
0239-sliding-window-maximum	Hard
0240-search-a-2d-matrix-ii	Medium
0332-reconstruct-itinerary	Hard
0347-top-k-frequent-elements	Medium
0349-intersection-of-two-arrays	Easy
0380-insert-delete-getrandom-o1	Medium
0561-array-partition	Easy
0622-design-circular-queue	Medium
0641-design-circular-deque	Medium
0704-binary-search	Easy
0706-design-hashmap	Easy
0739-daily-temperatures	Medium
0819-most-common-word	Easy
0937-reorder-data-in-log-files	Medium
0973-k-closest-points-to-origin	Medium
1046-last-stone-weight	Easy
3290-maximum-multiplication-score	Medium

Math

Problem Name	Difficulty
0002-add-two-numbers	Medium
0380-insert-delete-getrandom-o1	Medium
0973-k-closest-points-to-origin	Medium

Randomized

Problem Name	Difficulty
0380-insert-delete-getrandom-o1	Medium

Dynamic Programming

Problem Name	Difficulty
0005-longest-palindromic-substring	Medium
0042-trapping-rain-water	Hard
0121-best-time-to-buy-and-sell-stock	Easy
0122-best-time-to-buy-and-sell-stock-ii	Medium
0787-cheapest-flights-within-k-stops	Medium
3290-maximum-multiplication-score	Medium

Heap (Priority Queue)

Problem Name	Difficulty
0023-merge-k-sorted-lists	Hard
0215-kth-largest-element-in-an-array	Medium
0239-sliding-window-maximum	Hard
0332-reconstruct-itinerary	Hard
0347-top-k-frequent-elements	Medium
0743-network-delay-time	Medium
0787-cheapest-flights-within-k-stops	Medium
0973-k-closest-points-to-origin	Medium
1046-last-stone-weight	Easy

Recursion

Problem Name	Difficulty
0002-add-two-numbers	Medium
0021-merge-two-sorted-lists	Easy
0206-reverse-linked-list	Easy
0234-palindrome-linked-list	Easy

String

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0005-longest-palindromic-substring	Medium
0017-letter-combinations-of-a-phone-number	Medium
0020-valid-parentheses	Easy
0049-group-anagrams	Medium
0076-minimum-window-substring	Hard
0125-valid-palindrome	Easy
0316-remove-duplicate-letters	Medium
0332-reconstruct-itinerary	Hard
0344-reverse-string	Easy
0424-longest-repeating-character-replacement	Medium
0771-jewels-and-stones	Easy
0819-most-common-word	Easy
0937-reorder-data-in-log-files	Medium

Sliding Window

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0076-minimum-window-substring	Hard
0239-sliding-window-maximum	Hard
0424-longest-repeating-character-replacement	Medium

Binary Search

Problem Name	Difficulty
0004-median-of-two-sorted-arrays	Hard
0033-search-in-rotated-sorted-array	Medium
0167-two-sum-ii-input-array-is-sorted	Medium
0240-search-a-2d-matrix-ii	Medium
0349-intersection-of-two-arrays	Easy
0704-binary-search	Easy

Divide and Conquer

Problem Name	Difficulty
0004-median-of-two-sorted-arrays	Hard
0023-merge-k-sorted-lists	Hard
0215-kth-largest-element-in-an-array	Medium
0240-search-a-2d-matrix-ii	Medium
0347-top-k-frequent-elements	Medium
0973-k-closest-points-to-origin	Medium

Two Pointers

Problem Name	Difficulty
0005-longest-palindromic-substring	Medium
0011-container-with-most-water	Medium
0015-3sum	Medium
0042-trapping-rain-water	Hard
0125-valid-palindrome	Easy
0167-two-sum-ii-input-array-is-sorted	Medium
0234-palindrome-linked-list	Easy
0344-reverse-string	Easy
0349-intersection-of-two-arrays	Easy

Manacher

Problem Name	Difficulty
0005-longest-palindromic-substring	Medium

Greedy

Problem Name	Difficulty
0011-container-with-most-water	Medium
0122-best-time-to-buy-and-sell-stock-ii	Medium
0316-remove-duplicate-letters	Medium
0561-array-partition	Easy

Sorting

Problem Name	Difficulty
0015-3sum	Medium
0049-group-anagrams	Medium
0215-kth-largest-element-in-an-array	Medium
0332-reconstruct-itinerary	Hard
0347-top-k-frequent-elements	Medium
0349-intersection-of-two-arrays	Easy
0561-array-partition	Easy
0937-reorder-data-in-log-files	Medium
0973-k-closest-points-to-origin	Medium

Backtracking

Problem Name	Difficulty
0017-letter-combinations-of-a-phone-number	Medium
0039-combination-sum	Medium

Stack

Problem Name	Difficulty
0020-valid-parentheses	Easy
0042-trapping-rain-water	Hard
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy
0234-palindrome-linked-list	Easy
0316-remove-duplicate-letters	Medium
0739-daily-temperatures	Medium

Bracket Sequences

Problem Name	Difficulty
0020-valid-parentheses	Easy

Merge Sort

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

Tournament Sort

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

Monotonic Stack

Problem Name	Difficulty
0042-trapping-rain-water	Hard
0316-remove-duplicate-letters	Medium
0739-daily-temperatures	Medium

Depth-First Search

Problem Name	Difficulty
0200-number-of-islands	Medium
0207-course-schedule	Medium
0332-reconstruct-itinerary	Hard
0743-network-delay-time	Medium
0787-cheapest-flights-within-k-stops	Medium

Breadth-First Search

Problem Name	Difficulty
0200-number-of-islands	Medium
0207-course-schedule	Medium
0743-network-delay-time	Medium
0787-cheapest-flights-within-k-stops	Medium

Union-Find

Problem Name	Difficulty
0200-number-of-islands	Medium

Matrix

Problem Name	Difficulty
0200-number-of-islands	Medium
0240-search-a-2d-matrix-ii	Medium

Graph Theory

Problem Name	Difficulty
0207-course-schedule	Medium
0332-reconstruct-itinerary	Hard
0743-network-delay-time	Medium
0787-cheapest-flights-within-k-stops	Medium

Topological Sort

Problem Name	Difficulty
0207-course-schedule	Medium

Directed Acyclic Graph

Problem Name	Difficulty
0207-course-schedule	Medium

Queue

Problem Name	Difficulty
0225-implement-stack-using-queues	Easy
0232-implement-queue-using-stacks	Easy
0239-sliding-window-maximum	Hard
0622-design-circular-queue	Medium
0641-design-circular-deque	Medium

Prefix Sum

Problem Name	Difficulty
0238-product-of-array-except-self	Medium

Monotonic Queue

Problem Name	Difficulty
0239-sliding-window-maximum	Hard

Range Minimum/Maximum Query

Problem Name	Difficulty
0239-sliding-window-maximum	Hard

Eulerian Circuit

Problem Name	Difficulty
0332-reconstruct-itinerary	Hard

Eulerian Path

Problem Name	Difficulty
0332-reconstruct-itinerary	Hard

Semi-Eulerian Graph

Problem Name	Difficulty
0332-reconstruct-itinerary	Hard

Bucket Sort

Problem Name	Difficulty
0347-top-k-frequent-elements	Medium

Counting

Problem Name	Difficulty
0347-top-k-frequent-elements	Medium
0819-most-common-word	Easy

Quickselect

Problem Name	Difficulty
0215-kth-largest-element-in-an-array	Medium
0347-top-k-frequent-elements	Medium
0973-k-closest-points-to-origin	Medium

Counting Sort

Problem Name	Difficulty
0561-array-partition	Easy

Hash Function

Problem Name	Difficulty
0706-design-hashmap	Easy

Shortest Path

Problem Name	Difficulty
0743-network-delay-time	Medium
0787-cheapest-flights-within-k-stops	Medium

Dijkstra's Algorithm

Problem Name	Difficulty
0743-network-delay-time	Medium

Geometry

Problem Name	Difficulty
0973-k-closest-points-to-origin	Medium

K-D Tree

Problem Name	Difficulty
0973-k-closest-points-to-origin	Medium