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Merge Two Sorted Linked Lists

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Current Streak

0

Days

Challenge Bank

Arrays

20 Challenges

Best Time to Buy & Sell Stock

Easy
AmazonInfosysWiproArraySliding WindowGreedy
Solve

Find Duplicates in Array

Easy
TCSWiproCTSArrayHashSetSorting
Solve

Find the Missing Number

Easy
TCSInfosysWiproArrayMathBit Manipulation+ More
Solve

Maximum Subarray (Kadane's)

Easy
AmazonMicrosoftArrayDynamic ProgrammingDivide & Conquer
Solve

Move Zeroes to End

Easy
AccentureTCSArrayTwo PointersIn-place
Solve

Rotate Array by K Steps

Easy
MicrosoftAmazonArrayTwo PointersMath
Solve

Two Sum

Easy
AmazonGoogleFlipkartArrayHashMapTwo Pointers
Solve

Find Median of Two Sorted Arrays

Hard
GoogleFacebookArrayBinary SearchDivide & Conquer
Solve

Trapping Rainwater

Hard
GoogleAmazonMicrosoftArrayTwo PointersStack+ More
Solve

3Sum (Find All Triplets)

Medium
AmazonAdobeArrayTwo PointersSorting
Solve

Container With Most Water

Medium
AmazonGoogleArrayTwo PointersGreedy
Solve

Kth Largest Element

Medium
AmazonMicrosoftArrayHeapQuickSelect+ More
Solve

Longest Consecutive Sequence

Medium
GoogleFacebookArrayHashSet
Solve

Maximum Product Subarray

Medium
AmazonFlipkartArrayDynamic Programming
Solve

Merge Intervals

Medium
GoogleMicrosoftAmazonArraySortingIntervals
Solve

Next Permutation

Medium
AmazonMicrosoftArrayTwo PointersMath
Solve

Product of Array Except Self

Medium
AmazonGoogleFacebookArrayPrefix Product
Solve

Set Matrix Zeroes

Medium
MicrosoftAmazonArrayMatrix
Solve

Spiral Matrix Traversal

Medium
AmazonMicrosoftAdobeArrayMatrixSimulation
Solve

Subarray Sum Equals K

Medium
AmazonAdobeArrayHashMapPrefix Sum
Solve

Strings

15 Challenges

Check Palindrome

Easy
TCSWiproCTSStringTwo Pointers
Solve

Count and Say

Easy
GoogleAmazonStringSimulation
Solve

Longest Common Prefix

Easy
GoogleAmazonStringSortingTrie
Solve

Reverse a String

Easy
TCSWiproInfosysStringTwo Pointers
Solve

Roman to Integer

Easy
AmazonMicrosoftStringHashMapMath
Solve

String Compression

Easy
AccentureWiproStringTwo PointersIn-place
Solve

Valid Anagram

Easy
AmazonAdobeStringHashMapSorting
Solve

Valid Parentheses

Easy
AmazonMicrosoftStringStackHashMap
Solve

Minimum Window Substring

Hard
FacebookGoogleStringSliding WindowHashMap
Solve

Decode Ways

Medium
AmazonFacebookDynamic ProgrammingString
Solve

Group Anagrams

Medium
AmazonGoogleArrayHashMapString+ More
Solve

Integer to Roman

Medium
AmazonStringGreedyMath
Solve

Longest Palindromic Substring

Medium
AmazonMicrosoftFlipkartStringDynamic ProgrammingExpand Around Center
Solve

Longest Substring Without Repeating Chars

Medium
AmazonGoogleFacebookStringSliding WindowHashMap
Solve

Word Search in Grid

Medium
AmazonMicrosoftStringBacktrackingDFS+ More
Solve

Stacks & Queues

12 Challenges

Circular Queue Implementation

Easy
TCSWiproSee topic tags for pattern hints
Solve

Implement Queue using Two Stacks

Easy
TCSInfosysStackQueueDesign+ More
Solve

Implement Stack using Arrays

Easy
TCSWiproInfosysStackArrayData Structure Design
Solve

Implement Stack using Two Queues

Easy
TCSWiproQueueStackDesign
Solve

Basic Calculator

Hard
GoogleSee topic tags for pattern hints
Solve

Largest Rectangle in Histogram

Hard
AmazonGoogleSee topic tags for pattern hints
Solve

Sliding Window Maximum

Hard
AmazonGoogleSee topic tags for pattern hints
Solve

Daily Temperatures

Medium
AmazonStackMonotonic StackArray
Solve

Evaluate Reverse Polish Notation

Medium
AmazonStackMath
Solve

Min Stack (Get Minimum in O(1))

Medium
AmazonGoogleStackDesign
Solve

Next Greater Element

Medium
AmazonFlipkartStackMonotonic StackArray
Solve

Sort a Stack

Medium
AmazonAdobeSee topic tags for pattern hints
Solve

Trees

18 Challenges

Balanced Binary Tree Check

Easy
TCSAmazonTreeDFSRecursion
Solve

Binary Tree Traversals (Pre/In/Post)

Easy
TCSWiproAmazonTreeDFSRecursion+ More
Solve

Height of Binary Tree

Easy
TCSInfosysWiproTreeDFSBFS+ More
Solve

Mirror/Invert Binary Tree

Easy
AmazonGoogleTreeDFSBFS+ More
Solve

Path Sum in Binary Tree

Easy
AmazonMicrosoftTreeDFSRecursion
Solve

Symmetric Binary Tree

Easy
AmazonMicrosoftTreeDFSBFS+ More
Solve

Maximum Path Sum

Hard
AmazonGoogleFacebookSee topic tags for pattern hints
Solve

Serialize and Deserialize Tree

Hard
GoogleAmazonFacebookSee topic tags for pattern hints
Solve

Vertical Order Traversal

Hard
AmazonGoogleSee topic tags for pattern hints
Solve

Binary Tree Right Side View

Medium
AmazonFacebookSee topic tags for pattern hints
Solve

Check if BST is Valid

Medium
AmazonMicrosoftAdobeTreeDFSRecursion+ More
Solve

Construct Tree from Preorder+Inorder

Medium
AmazonMicrosoftSee topic tags for pattern hints
Solve

Count Nodes in Complete Binary Tree

Medium
AmazonSee topic tags for pattern hints
Solve

Diameter of Binary Tree

Medium
AmazonAdobeTreeDFSRecursion
Solve

Flatten Tree to Linked List

Medium
AmazonMicrosoftSee topic tags for pattern hints
Solve

Kth Smallest in BST

Medium
AmazonMicrosoftSee topic tags for pattern hints
Solve

Level Order Traversal (BFS)

Medium
AmazonMicrosoftTreeBFSQueue+ More
Solve

Lowest Common Ancestor

Medium
AmazonMicrosoftFacebookTreeDFSRecursion
Solve

Graphs

12 Challenges

BFS Traversal

Easy
TCSWiproAmazonGraphBFSQueue
Solve

DFS Traversal

Easy
TCSWiproAmazonGraphDFSStack+ More
Solve

Flood Fill Algorithm

Easy
AmazonAdobeGraphBFSDFS+ More
Solve

Find Bridges in Graph

Hard
GoogleSee topic tags for pattern hints
Solve

Word Ladder

Hard
AmazonGoogleSee topic tags for pattern hints
Solve

Clone Graph

Medium
AmazonFacebookSee topic tags for pattern hints
Solve

Course Schedule (Cycle Detection)

Medium
AmazonMicrosoftGoogleGraphTopological SortBFS+ More
Solve

Detect Cycle in Directed Graph

Medium
AmazonMicrosoftGraphDFSCycle Detection+ More
Solve

Detect Cycle in Undirected Graph

Medium
AmazonMicrosoftGraphDFSUnion-Find+ More
Solve

Number of Islands

Medium
AmazonGoogleFacebookGraphBFSDFS+ More
Solve

Shortest Path Dijkstra

Medium
AmazonMicrosoftGoogleGraphGreedyPriority Queue+ More
Solve

Topological Sort

Medium
AmazonGoogleGraphBFSDFS+ More
Solve

Dynamic Programming

20 Challenges

Climbing Stairs

Easy
AmazonGoogleAdobeDynamic ProgrammingFibonacci
Solve

Fibonacci (Memoization + Tabulation)

Easy
TCSWiproInfosysDynamic ProgrammingRecursionMemoization
Solve

Burst Balloons

Hard
GoogleFacebookSee topic tags for pattern hints
Solve

Edit Distance (Levenshtein)

Hard
AmazonGoogleMicrosoftDynamic ProgrammingStringLCS
Solve

Matrix Chain Multiplication

Hard
TCSAmazonGoogleDynamic ProgrammingInterval DP
Solve

Palindrome Partitioning

Hard
AmazonGoogleRecursionBacktrackingDynamic Programming
Solve

Regular Expression Matching

Hard
GoogleFacebookDynamic ProgrammingStringBacktracking
Solve

Wildcard Pattern Matching

Hard
AmazonGoogleDynamic ProgrammingStringGreedy
Solve

0/1 Knapsack

Medium
AmazonMicrosoftTCSDynamic ProgrammingKnapsack
Solve

Coin Change (Minimum Coins)

Medium
AmazonGoogleMicrosoftDynamic ProgrammingKnapsackBFS
Solve

House Robber

Medium
AmazonMicrosoftDynamic ProgrammingFibonacci
Solve

Jump Game

Medium
AmazonMicrosoftArrayGreedyDynamic Programming
Solve

Longest Common Subsequence

Medium
AmazonGoogleAdobeDynamic ProgrammingLCSString
Solve

Longest Increasing Subsequence

Medium
AmazonMicrosoftDynamic ProgrammingBinary SearchPatience Sorting
Solve

Minimum Cost to Cut a Rod

Medium
AmazonTCSDynamic ProgrammingKnapsack
Solve

Minimum Path Sum in Grid

Medium
AmazonGoogleDynamic ProgrammingMatrix
Solve

Partition Equal Subset Sum

Medium
AmazonFacebookDynamic ProgrammingKnapsack
Solve

Subset Sum Problem

Medium
AmazonTCSFlipkartDynamic ProgrammingKnapsack
Solve

Unique Paths in Grid

Medium
AmazonGoogleDynamic ProgrammingMathCombinatorics
Solve

Word Break Problem

Medium
AmazonGoogleFacebookDynamic ProgrammingStringHashSet+ More
Solve

Binary Search

8 Challenges

Binary Search

Easy
TCSWiproAmazonArrayBinary SearchDivide & Conquer
Solve

Kth Smallest in Sorted Matrix

Hard
AmazonGoogleArrayBinary SearchHeap
Solve

Aggressive Cows (Binary Search on Answer)

Medium
AmazonGoogleArrayBinary SearchGreedy
Solve

Book Allocation Problem

Medium
AmazonAdobeArrayBinary SearchGreedy
Solve

Find Minimum in Rotated Array

Medium
AmazonMicrosoftArrayBinary SearchDivide & Conquer
Solve

Find Peak Element

Medium
GoogleAmazonArrayBinary SearchDivide & Conquer
Solve

Search in 2D Matrix

Medium
AmazonMicrosoftArrayBinary SearchMatrix
Solve

Search in Rotated Sorted Array

Medium
AmazonMicrosoftFacebookArrayBinary Search
Solve

Hashing

7 Challenges

Ransom Note Check

Easy
AmazonStringHashMapArray
Solve

Two Sum using HashMap

Easy
AmazonTCSArrayHashMap
Solve

Four Sum Problem

Hard
AmazonGoogleArrayTwo PointersSorting
Solve

Count Distinct Elements in Window

Medium
AmazonGoogleArraySliding WindowHashMap
Solve

Largest Subarray with Sum 0

Medium
AmazonAdobeArrayHashMapPrefix Sum
Solve

Longest Consecutive Subsequence

Medium
AmazonGoogleArrayHashSet
Solve

Top K Frequent Elements

Medium
AmazonFacebookArrayHashMapHeap+ More
Solve

Linked Lists

15 Challenges

Detect Cycle in Linked List

Easy
AmazonMicrosoftLinked ListTwo PointersFloyds Algorithm
Solve

Find Middle of Linked List

Easy
TCSInfosysLinked ListTwo PointersFast and Slow
Solve

Merge Two Sorted Linked Lists

Easy
AmazonMicrosoftFlipkartLinked ListTwo PointersRecursion
Solve

Palindrome Linked List

Easy
AmazonLinked ListTwo PointersFast & Slow
Solve

Reverse Linked List

Easy
TCSWiproAmazonLinked ListIterativeRecursion
Solve

LRU Cache Implementation

Hard
AmazonGoogleMicrosoftDesignHashMapDoubly Linked List
Solve

Add Two Numbers as Linked Lists

Medium
AmazonMicrosoftLinked ListMathSimulation
Solve

Copy List with Random Pointer

Medium
AmazonMicrosoftSee topic tags for pattern hints
Solve

Flatten Multilevel Doubly Linked List

Medium
MicrosoftSee topic tags for pattern hints
Solve

Intersection of Two Linked Lists

Medium
AmazonMicrosoftLinked ListTwo PointersHashSet
Solve

Remove Nth Node From End

Medium
AmazonMicrosoftLinked ListTwo PointersFast & Slow
Solve

Reorder Linked List

Medium
AmazonSee topic tags for pattern hints
Solve

Rotate Linked List by K

Medium
AmazonMicrosoftSee topic tags for pattern hints
Solve

Sort Linked List (Merge Sort)

Medium
AmazonMicrosoftSee topic tags for pattern hints
Solve

Swap Nodes in Pairs

Medium
AmazonSee topic tags for pattern hints
Solve

Recursion & Backtracking

8 Challenges

Fibonacci using Recursion

Easy
TCSWiproInfosysRecursionMemoizationDynamic Programming
Solve

Tower of Hanoi

Easy
TCSWiproRecursionDivide & Conquer
Solve

N-Queens Problem

Hard
AmazonGoogleRecursionBacktracking
Solve

Sudoku Solver

Hard
AmazonGoogleMicrosoftRecursionBacktracking
Solve

Letter Combinations Phone Number

Medium
AmazonGoogleRecursionBacktrackingString
Solve

Permutations of a String

Medium
AmazonTCSAdobeRecursionBacktrackingString
Solve

Rat in a Maze

Medium
TCSWiproAmazonRecursionBacktrackingMatrix
Solve

Subsets / Power Set

Medium
AmazonFacebookRecursionBacktrackingBit Manipulation
Solve

Sorting

10 Challenges

Bubble Sort

Easy
TCSWiproInfosysSortingArrayComparison Sort
Solve

Count Sort

Easy
AmazonAdobeSortingCountingArray
Solve

Insertion Sort

Easy
TCSWiproInfosysSortingArrayComparison Sort
Solve

Selection Sort

Easy
TCSWiproInfosysSortingArrayComparison Sort
Solve

Count Inversions in Array

Medium
AmazonGoogleSortingDivide & ConquerMerge Sort
Solve

Heap Sort

Medium
AmazonMicrosoftSortingHeapArray
Solve

Merge Sort

Medium
AmazonMicrosoftTCSSortingDivide & ConquerRecursion+ More
Solve

Quick Sort

Medium
AmazonMicrosoftTCSSortingDivide & ConquerRecursion
Solve

Radix Sort

Medium
GoogleSortingCounting SortRadix
Solve

Sort Colors (Dutch National Flag)

Medium
AmazonMicrosoftArrayTwo PointersDutch National Flag
Solve

Tries

5 Challenges

Longest Common Prefix using Trie

Easy
GoogleAmazonTrieString
Solve

Maximum XOR using Trie

Hard
GoogleCodeforcesTrieBit Manipulation
Solve

Word Dictionary with Wildcard

Hard
FacebookTrieDFSBacktracking+ More
Solve

Implement Trie (Prefix Tree)

Medium
AmazonGoogleMicrosoftTrieDesignString
Solve

Search Suggestions System

Medium
AmazonTrieBinary SearchString
Solve