LeetCode Problems by Pattern

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Problems are organized by common patterns and sorted by difficulty. Click any problem to practice on LeetCode. Remember to follow the study tips from the main guide!

HashMaps

Easy

Two Sum Valid Anagram Contains Duplicate Intersection of Two Arrays First Unique Character in a String Ransom Note Jewels and Stones Majority Element

Medium

Group Anagrams Subarray Sum Equals K Longest Substring Without Repeating Characters Top K Frequent Elements 4Sum II Longest Palindrome by Concatenating Two Letter Words Partition Labels

Hard

Minimum Window Substring Substring with Concatenation of All Words Count of Smaller Numbers After Self

Recursion

Easy

Reverse String Pascal's Triangle Fibonacci Number Power of Three Maximum Depth of Binary Tree

Medium

Combination Sum Permutations Generate Parentheses Word Search Letter Combinations of a Phone Number Subset II

Hard

N-Queens Sudoku Solver Word Squares

DFS & BFS

Easy

Flood Fill Island Perimeter Maximum Depth of Binary Tree Symmetric Tree

Medium

Number of Islands Word Ladder Clone Graph Pacific Atlantic Water Flow Surrounded Regions Course Schedule

Hard

Shortest Path in a Grid with Obstacles Elimination Word Ladder II Cut Off Trees for Golf Event

Binary Search

Easy

Binary Search Guess Number Higher or Lower Find Smallest Letter Greater Than Target Intersection of Two Arrays II

Medium

Search in Rotated Sorted Array Find Peak Element Search a 2D Matrix Koko Eating Bananas Split Array Largest Sum

Hard

Median of Two Sorted Arrays Find Minimum in Rotated Sorted Array II Maximum Profit in Job Scheduling

Sliding Window

Easy

Maximum Average Subarray I Longest Continuous Subarray with Absolute Diff Less Than or Equal to Limit Permutation in String

Medium

Longest Substring Without Repeating Characters Sliding Window Maximum Fruit Into Baskets Subarrays with K Different Integers Minimum Size Subarray Sum

Hard

Longest Substring with At Most K Distinct Characters Count Vowel Substrings of a Given String

Heaps

Easy

Kth Largest Element in a Stream Last Stone Weight

Medium

Top K Frequent Elements K Closest Points to Origin Sort Characters by Frequency Task Scheduler

Hard

Find Median from Data Stream Merge K Sorted Lists Sliding Window Median