leetcode

A collection of solutions to selected LeetCode problems.

LeetCode Topics

Stack

Problem Name	Difficulty
0042-trapping-rain-water	Hard
0155-min-stack	Medium
0232-implement-queue-using-stacks	Easy

Design

Problem Name	Difficulty
0155-min-stack	Medium
0208-implement-trie-prefix-tree	Medium
0232-implement-queue-using-stacks	Easy
0295-find-median-from-data-stream	Hard
0297-serialize-and-deserialize-binary-tree	Hard
0981-time-based-key-value-store	Medium

Queue

Problem Name	Difficulty
0232-implement-queue-using-stacks	Easy

Hash Table

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0076-minimum-window-substring	Hard
0133-clone-graph	Medium
0169-majority-element	Easy
0208-implement-trie-prefix-tree	Medium
0242-valid-anagram	Easy
0409-longest-palindrome	Easy
0981-time-based-key-value-store	Medium

Depth-First Search

Problem Name	Difficulty
0098-validate-binary-search-tree	Medium
0110-balanced-binary-tree	Easy
0133-clone-graph	Medium
0200-number-of-islands	Medium
0207-course-schedule	Medium
0226-invert-binary-tree	Easy
0235-lowest-common-ancestor-of-a-binary-search-tree	Medium
0236-lowest-common-ancestor-of-a-binary-tree	Medium
0297-serialize-and-deserialize-binary-tree	Hard
0543-diameter-of-binary-tree	Easy

Breadth-First Search

Problem Name	Difficulty
0102-binary-tree-level-order-traversal	Medium
0133-clone-graph	Medium
0200-number-of-islands	Medium
0207-course-schedule	Medium
0226-invert-binary-tree	Easy
0297-serialize-and-deserialize-binary-tree	Hard
0322-coin-change	Medium
0542-01-matrix	Medium
0994-rotting-oranges	Medium

Graph Theory

Problem Name	Difficulty
0133-clone-graph	Medium
0207-course-schedule	Medium

String

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0067-add-binary	Easy
0076-minimum-window-substring	Hard
0208-implement-trie-prefix-tree	Medium
0242-valid-anagram	Easy
0297-serialize-and-deserialize-binary-tree	Hard
0409-longest-palindrome	Easy
0981-time-based-key-value-store	Medium

Sliding Window

Problem Name	Difficulty
0003-longest-substring-without-repeating-characters	Medium
0076-minimum-window-substring	Hard

Topological Sort

Problem Name	Difficulty
0207-course-schedule	Medium

Tree

Problem Name	Difficulty
0098-validate-binary-search-tree	Medium
0102-binary-tree-level-order-traversal	Medium
0110-balanced-binary-tree	Easy
0226-invert-binary-tree	Easy
0235-lowest-common-ancestor-of-a-binary-search-tree	Medium
0236-lowest-common-ancestor-of-a-binary-tree	Medium
0297-serialize-and-deserialize-binary-tree	Hard
0543-diameter-of-binary-tree	Easy

Binary Tree

Problem Name	Difficulty
0098-validate-binary-search-tree	Medium
0102-binary-tree-level-order-traversal	Medium
0110-balanced-binary-tree	Easy
0226-invert-binary-tree	Easy
0235-lowest-common-ancestor-of-a-binary-search-tree	Medium
0236-lowest-common-ancestor-of-a-binary-tree	Medium
0297-serialize-and-deserialize-binary-tree	Hard
0543-diameter-of-binary-tree	Easy

Two Pointers

Problem Name	Difficulty
0015-3sum	Medium
0042-trapping-rain-water	Hard
0295-find-median-from-data-stream	Hard
0876-middle-of-the-linked-list	Easy

Sorting

Problem Name	Difficulty
0015-3sum	Medium
0056-merge-intervals	Medium
0169-majority-element	Easy
0242-valid-anagram	Easy
0295-find-median-from-data-stream	Hard

Heap (Priority Queue)

Problem Name	Difficulty
0295-find-median-from-data-stream	Hard

Data Stream

Problem Name	Difficulty
0295-find-median-from-data-stream	Hard

Array

Problem Name	Difficulty
0015-3sum	Medium
0033-search-in-rotated-sorted-array	Medium
0039-combination-sum	Medium
0042-trapping-rain-water	Hard
0046-permutations	Medium
0053-maximum-subarray	Medium
0056-merge-intervals	Medium
0057-insert-interval	Medium
0121-best-time-to-buy-and-sell-stock	Easy
0169-majority-element	Easy
0200-number-of-islands	Medium
0238-product-of-array-except-self	Medium
0322-coin-change	Medium
0542-01-matrix	Medium
0994-rotting-oranges	Medium

Dynamic Programming

Problem Name	Difficulty
0042-trapping-rain-water	Hard
0053-maximum-subarray	Medium
0070-climbing-stairs	Easy
0121-best-time-to-buy-and-sell-stock	Easy
0322-coin-change	Medium
0542-01-matrix	Medium

Backtracking

Problem Name	Difficulty
0039-combination-sum	Medium
0046-permutations	Medium

Divide and Conquer

Problem Name	Difficulty
0053-maximum-subarray	Medium
0169-majority-element	Easy

Counting

Problem Name	Difficulty
0169-majority-element	Easy

Union-Find

Problem Name	Difficulty
0200-number-of-islands	Medium

Matrix

Problem Name	Difficulty
0200-number-of-islands	Medium
0542-01-matrix	Medium
0994-rotting-oranges	Medium

Binary Search

Problem Name	Difficulty
0033-search-in-rotated-sorted-array	Medium
0981-time-based-key-value-store	Medium

Prefix Sum

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

Monotonic Stack

Problem Name	Difficulty
0042-trapping-rain-water	Hard

Math

Problem Name	Difficulty
0067-add-binary	Easy
0070-climbing-stairs	Easy

Memoization

Problem Name	Difficulty
0070-climbing-stairs	Easy

Trie

Problem Name	Difficulty
0208-implement-trie-prefix-tree	Medium

Greedy

Problem Name	Difficulty
0409-longest-palindrome	Easy

Linked List

Problem Name	Difficulty
0021-merge-two-sorted-lists	Easy
0206-reverse-linked-list	Easy
0876-middle-of-the-linked-list	Easy

Recursion

Problem Name	Difficulty
0021-merge-two-sorted-lists	Easy
0206-reverse-linked-list	Easy

Bit Manipulation

Problem Name	Difficulty
0067-add-binary	Easy

Simulation

Problem Name	Difficulty
0067-add-binary	Easy

Binary Search Tree

Problem Name	Difficulty
0098-validate-binary-search-tree	Medium
0235-lowest-common-ancestor-of-a-binary-search-tree	Medium