Practice

Problems grouped by difficulty and pattern. Hide the pattern name and use “What pattern is this?” mode to test recognition: read the statement, constraints and examples, commit to an approach, then see the clues.

Hide pattern names

103 problems · quiz score 0/0

Two Sumeasy Group Anagramsmedium Design HashMapeasy Insert Delete GetRandom O(1)medium Repeated DNA Sequencesmedium Longest Substring Without Repeating Charactersmedium Minimum Window Substringhard Max Consecutive Ones IIImedium Longest Repeating Character Replacementmedium Fruit Into Basketsmedium Permutation in Stringmedium Sliding Window Maximumhard 3Summedium Container With Most Watermedium Two Sum II — Sorted Inputeasy Remove Duplicates from Sorted Arrayeasy Move Zeroeseasy Sort Colors (Dutch National Flag)medium Trapping Rain Waterhard Interval List Intersectionsmedium Linked List Cycleeasy Middle of the Linked Listeasy Find the Duplicate Numbermedium Reverse Linked Listeasy LRU Cachemedium Merge k Sorted Listshard Search in Rotated Sorted Arraymedium Koko Eating Bananasmedium Kth Smallest Element in a BSTmedium Subarray Sum Equals Kmedium Product of Array Except Selfmedium Corporate Flight Bookingsmedium Range Sum Query 2D — Immutablemedium Valid Parentheseseasy Min Stackmedium Daily Temperaturesmedium Next Greater Elementeasy Largest Rectangle in Histogramhard Car Fleetmedium Kth Largest Element in an Arraymedium Top K Frequent Elementsmedium Kth Largest Element in a Streameasy Find Median from Data Streamhard Task Schedulermedium Meeting Rooms IImedium Merge Intervalsmedium Non-overlapping Intervalsmedium Number of Islandsmedium Binary Tree Level Order Traversalmedium Word Ladderhard Shortest Path in Binary Matrixmedium Rotting Orangesmedium Clone Graphmedium Shortest Path Visiting All Nodeshard Number of Connected Componentsmedium Is Graph Bipartite?medium Critical Connections in a Networkhard Reconstruct Itineraryhard Network Delay Timemedium Cheapest Flights Within K Stopsmedium Min Cost to Connect All Pointsmedium Redundant Connectionmedium Course Schedulemedium Alien Dictionaryhard Validate Binary Search Treemedium Lowest Common Ancestor of a Binary Treemedium Binary Tree Maximum Path Sumhard Serialize and Deserialize Binary Treehard N-Queenshard Subsetsmedium Permutationsmedium Combination Summedium Word Searchmedium Sudoku Solverhard Implement Trie (Prefix Tree)medium Word Search IIhard Climbing Stairseasy House Robbermedium Coin Changemedium Word Breakmedium Longest Increasing Subsequencemedium Longest Common Subsequencemedium Edit Distancemedium Partition Equal Subset Summedium Unique Pathsmedium Longest Palindromic Substringmedium Burst Balloonshard Matrix Chain Multiplicationhard Maximum Subarraymedium Gas Stationmedium Jump Gamemedium Activity Selectioneasy Fractional Knapsackeasy Job Sequencing with Deadlinesmedium Huffman Codingmedium Pow(x, n)medium Count Primesmedium Single Numbereasy Counting Bitseasy Bit Counting Trickseasy Range Sum Query — Mutablemedium Range XOR Queries with Updatesmedium Find the Index of the First Occurrenceeasy