•PRACTICE

DSA Question Tracker & Breakdowns

The problems top tech companies actually ask, each with a full breakdown, diagrams and code. Tick them off as you go, or browse by topic.

433problems
32companies
39topics
3languages each

Companies

Amazon80Microsoft79Google76Meta76Apple73Uber64Walmart54Atlassian52Bloomberg51Oracle49Salesforce49Goldman Sachs39TikTok34Netflix32Databricks25LinkedIn24Visa23Anduril21Rippling21Snowflake20Adobe16NVIDIA16DE Shaw14JPMorgan14OpenAI14Pinterest14Capital One12Roblox11Airbnb9Flipkart9Anthropic4Ripple4

Topics

Array 240Hash Table 113String 112Depth-First Search 73Sorting 66Dynamic Programming 65Breadth-First Search 56Math 49Design 46Binary Search 44Greedy 43Tree 41Two Pointers 39Heap 35Stack 32Graph 28Matrix 28Sliding Window 26Binary Tree 23Backtracking 22Bit Manipulation 20Prefix Sum 20Simulation 20Union Find 19Linked List 18Queue 13Trie 12Counting 10Recursion 10Divide and Conquer 9Monotonic Stack 9Ordered Set 9Topological Sort 9Data Stream 8Database 6Enumeration 6Binary Search Tree 5Doubly-Linked List 5Geometry 5
1.Two Sum
ArrayHash Table
Easy+10▶ Mock
3.Longest Substring Without Repeating Characters
Hash TableStringSliding Window
Medium+13▶ Mock
56.Merge Intervals
ArraySorting
Medium+14▶ Mock
121.Best Time to Buy and Sell Stock
ArrayDynamic Programming
Easy+10▶ Mock
5.Longest Palindromic Substring
StringDynamic Programming
Medium+8▶ Mock
49.Group Anagrams
Hash TableStringSorting
Medium+9▶ Mock
15.3Sum
ArrayTwo PointersSorting
Medium+5▶ Mock
11.Container With Most Water
ArrayTwo PointersGreedy
Medium+6▶ Mock
42.Trapping Rain Water
ArrayTwo PointersStack
Hard+6▶ Mock
4.Median of Two Sorted Arrays
ArrayBinary SearchDivide and Conquer
Hard+5▶ Mock
347.Top K Frequent Elements
ArrayHash TableHeap
Medium+6▶ Mock
2.Add Two Numbers
Linked ListMathRecursion
Medium+3▶ Mock
994.Rotting Oranges
Breadth-First SearchMatrixQueue
Medium+5▶ Mock
128.Longest Consecutive Sequence
ArrayHash TableUnion Find
Medium+3▶ Mock
23.Merge k Sorted Lists
Linked ListHeapDivide and Conquer
Hard+4▶ Mock
21.Merge Two Sorted Lists
Linked ListRecursion
Easy+2▶ Mock
200.Number of Islands
Depth-First SearchBreadth-First SearchMatrix
Medium+7▶ Mock
20.Valid Parentheses
StackString
Easy+3▶ Mock
198.House Robber
Dynamic ProgrammingArray
Medium+1▶ Mock
210.Course Schedule II
Depth-First SearchBreadth-First SearchGraph
Medium+3▶ Mock
560.Subarray Sum Equals K
ArrayHash TablePrefix Sum
Medium+2▶ Mock
33.Search in Rotated Sorted Array
ArrayBinary Search
Medium+5▶ Mock
207.Course Schedule
Depth-First SearchBreadth-First SearchGraph
Medium+4▶ Mock
206.Reverse Linked List
Linked ListRecursion
Easy+4▶ Mock
146.LRU Cache
Hash TableLinked ListDesign
Medium+9▶ Mock
102.Binary Tree Level Order Traversal
Breadth-First SearchTree
Medium+4▶ Mock
98.Validate Binary Search Tree
Depth-First SearchBinary Search TreeTree
Medium+3▶ Mock
104.Maximum Depth of Binary Tree
Depth-First SearchBreadth-First SearchTree
Easy+4▶ Mock
226.Invert Binary Tree
Depth-First SearchBreadth-First SearchTree
Easy+1▶ Mock
100.Same Tree
Depth-First SearchBreadth-First SearchTree
Easy+2▶ Mock
101.Symmetric Tree
Depth-First SearchBreadth-First SearchTree
Easy+1▶ Mock
70.Climbing Stairs
Dynamic ProgrammingMath
Easy+4▶ Mock
53.Maximum Subarray
ArrayDynamic ProgrammingDivide and Conquer
Medium+7▶ Mock
322.Coin Change
Dynamic ProgrammingBreadth-First Search
Medium+4▶ Mock
139.Word Break
Dynamic ProgrammingHash TableTrie
Medium+5▶ Mock
238.Product of Array Except Self
ArrayPrefix Sum
Medium+5▶ Mock
739.Daily Temperatures
StackArray
Medium+4▶ Mock
438.Find All Anagrams in a String
Hash TableStringSliding Window
Medium+2▶ Mock
Implement Trie (Prefix Tree)
TrieDesignString
Medium+2▶ Mock
Design Add and Search Words Data Structure
TrieDepth-First SearchDesign
Medium+1▶ Mock
269.Alien Dictionary
GraphTopological SortDepth-First Search
Hard+2▶ Mock
253.Meeting Rooms II
ArrayHeapSorting
Medium+6▶ Mock
230.Kth Smallest Element in a BST
Depth-First SearchBinary Search TreeTree
Medium+2▶ Mock
236.Lowest Common Ancestor of a Binary Tree
Depth-First SearchTree
Medium+4▶ Mock
91.Decode Ways
Dynamic ProgrammingString
Medium+4▶ Mock
133.Clone Graph
Depth-First SearchBreadth-First SearchGraph
Medium+1▶ Mock
134.Gas Station
ArrayGreedy
Medium+5▶ Mock
621.Task Scheduler
GreedyHeapHash Table
Medium+2▶ Mock
152.Maximum Product Subarray
ArrayDynamic Programming
Medium+4▶ Mock
295.Find Median from Data Stream
HeapDesignData Stream
Hard+6▶ Mock
297.Serialize and Deserialize Binary Tree
Depth-First SearchBreadth-First SearchTree
Hard+4▶ Mock
283.Move Zeroes
ArrayTwo Pointers
Easy▶ Mock
45.Jump Game II
ArrayDynamic ProgrammingGreedy
Medium▶ Mock
460.LFU Cache
Hash TableLinked ListDesign
Hard+1▶ Mock
34.Find First and Last Position of Element in Sorted Array
ArrayBinary Search
Medium+1▶ Mock
22.Generate Parentheses
StringDynamic ProgrammingBacktracking
Medium+1▶ Mock
1146.Snapshot Array
ArrayHash TableBinary Search
Medium▶ Mock
7.Reverse Integer
Math
Medium▶ Mock
567.Permutation in String
Hash TableTwo PointersString
Medium▶ Mock
75.Sort Colors
ArrayTwo PointersSorting
Medium▶ Mock
341.Flatten Nested List Iterator
StackTreeDepth-First Search
Medium▶ Mock
981.Time Based Key-Value Store
Hash TableStringBinary Search
Medium+1▶ Mock
14.Longest Common Prefix
ArrayStringTrie
Easy+1▶ Mock
76.Minimum Window Substring
Hash TableStringSliding Window
Hard▶ Mock
26.Remove Duplicates from Sorted Array
ArrayTwo Pointers
Easy+1▶ Mock
79.Word Search
ArrayStringBacktracking
Medium+1▶ Mock
13.Roman to Integer
Hash TableMathString
Easy+1▶ Mock
189.Rotate Array
ArrayMathTwo Pointers
Medium+1▶ Mock
88.Merge Sorted Array
ArrayTwo PointersSorting
Easy+1▶ Mock
54.Spiral Matrix
ArrayMatrixSimulation
Medium+2▶ Mock
17.Letter Combinations of a Phone Number
Hash TableStringBacktracking
Medium+1▶ Mock
12.Integer to Roman
Hash TableMathString
Medium▶ Mock
78.Subsets
ArrayBacktrackingBit Manipulation
Medium▶ Mock
215.Kth Largest Element in an Array
ArrayDivide and ConquerSorting
Medium▶ Mock
122.Best Time to Buy and Sell Stock II
ArrayDynamic ProgrammingGreedy
Medium▶ Mock
399.Evaluate Division
ArrayStringDepth-First Search
Medium▶ Mock
44.Wildcard Matching
StringDynamic ProgrammingGreedy
Hard▶ Mock
380.Insert Delete GetRandom O(1)
ArrayHash TableMath
Medium▶ Mock
2858.Minimum Edge Reversals So Every Node Is Reachable
Dynamic ProgrammingDepth-First SearchBreadth-First Search
Hard▶ Mock
721.Accounts Merge
ArrayHash TableString
Medium▶ Mock
2502.Design Memory Allocator
ArrayHash TableDesign
Medium+1▶ Mock
239.Sliding Window Maximum
ArrayQueueSliding Window
Hard+2▶ Mock
9.Palindrome Number
Math
Easy▶ Mock
1929.Concatenation of Array
ArraySimulation
Easy▶ Mock
904.Fruit Into Baskets
ArrayHash TableSliding Window
Medium▶ Mock
167.Two Sum II - Input Array Is Sorted
ArrayTwo PointersBinary Search
Medium▶ Mock
125.Valid Palindrome
Two PointersString
Easy▶ Mock
8.String to Integer (atoi)
String
Medium▶ Mock
50.Pow(x, n)
MathRecursion
Medium▶ Mock
977.Squares of a Sorted Array
ArrayTwo PointersSorting
Easy▶ Mock
31.Next Permutation
ArrayTwo Pointers
Medium▶ Mock
875.Koko Eating Bananas
ArrayBinary Search
Medium▶ Mock
735.Asteroid Collision
ArrayStackSimulation
Medium+1▶ Mock
169.Majority Element
ArrayHash TableDivide and Conquer
Easy▶ Mock
2571.Minimum Operations to Reduce an Integer to 0
Dynamic ProgrammingGreedyBit Manipulation
Medium▶ Mock
362.Design Hit Counter
ArrayBinary SearchDesign
Medium▶ Mock
410.Split Array Largest Sum
ArrayBinary SearchDynamic Programming
Hard▶ Mock
41.First Missing Positive
ArrayHash Table
Hard▶ Mock
124.Binary Tree Maximum Path Sum
Dynamic ProgrammingTreeDepth-First Search
Hard▶ Mock
155.Min Stack
StackDesign
Medium▶ Mock
138.Copy List with Random Pointer
Hash TableLinked List
Medium+1▶ Mock
Employees Earning More Than Their Managers
Database
Easy▶ Mock
Recyclable and Low Fat Products
Database
Easy▶ Mock
2639.Find the Width of Columns of a Grid
ArrayMatrix
Easy▶ Mock
2408.Design SQL
ArrayHash TableString
Medium▶ Mock
2035.Partition Array Into Two Arrays to Minimize Sum Difference
ArrayBinary SearchDynamic Programming
Hard▶ Mock
2503.Maximum Number of Points from Grid Queries
ArrayTwo PointersBreadth-First Search
Hard▶ Mock
1962.Remove Stones to Minimize the Total
ArrayGreedyHeap
Medium▶ Mock
67.Add Binary
MathStringBit Manipulation
Easy▶ Mock
3471.Find the Largest Almost Missing Integer
ArrayHash Table
Easy▶ Mock
40.Combination Sum II
ArrayBacktracking
Medium▶ Mock
235.Lowest Common Ancestor of a Binary Search Tree
TreeDepth-First SearchBinary Search Tree
Medium▶ Mock
516.Longest Palindromic Subsequence
StringDynamic Programming
Medium▶ Mock
1091.Shortest Path in a Binary Matrix
ArrayBreadth-First SearchMatrix
Medium▶ Mock
1429.First Unique Number
ArrayHash TableDesign
Medium▶ Mock
424.Longest Repeating Character Replacement
Hash TableStringSliding Window
Medium▶ Mock
704.Binary Search
ArrayBinary Search
Easy▶ Mock
300.Longest Increasing Subsequence
ArrayBinary SearchDynamic Programming
Medium▶ Mock
1049.Last Stone Weight II
ArrayDynamic ProgrammingKnapsack
Medium▶ Mock
503.Next Greater Element II
ArrayStackMonotonic Stack
Medium▶ Mock
2939.Maximum XOR Product
MathGreedyBit Manipulation
Medium▶ Mock
303.Range Sum Query - Immutable
ArrayDesignPrefix Sum
Easy▶ Mock
1797.Design Authentication Manager
Hash TableLinked ListDesign
Medium▶ Mock
2402.Meeting Rooms III
ArrayHash TableSorting
Hard▶ Mock
103.Binary Tree Zigzag Level Order Traversal
TreeBreadth-First SearchBinary Tree
Medium▶ Mock
48.Rotate Image
ArrayMathMatrix
Medium▶ Mock
1197.Minimum Knight Moves
Breadth-First SearchHeuristic Search
Medium▶ Mock
1143.Longest Common Subsequence
StringDynamic Programming
Medium▶ Mock
751.IP to CIDR
StringBit Manipulation
Medium▶ Mock
6.Zigzag Conversion
String
Medium▶ Mock
1046.Last Stone Weight
ArrayHeap
Easy▶ Mock
127.Word Ladder
Hash TableStringBreadth-First Search
Hard▶ Mock
219.Contains Duplicate II
ArrayHash TableSliding Window
Easy▶ Mock
1335.Minimum Difficulty of a Job Schedule
ArrayDynamic Programming
Hard▶ Mock
68.Text Justification
ArrayStringSimulation
Hard▶ Mock
359.Design Logger Rate Limiter
Hash TableDesignData Stream
Easy▶ Mock
217.Contains Duplicate
ArrayHash TableSorting
Easy▶ Mock
39.Combination Sum
ArrayBacktracking
Medium▶ Mock
430.Flatten a Multilevel Doubly Linked List
Linked ListDepth-First SearchDoubly-Linked List
Medium▶ Mock
1839.Longest Substring Of All Vowels in Order
StringSliding Window
Medium▶ Mock
2477.Minimum Fuel Cost to Report to the Capital
TreeDepth-First SearchBreadth-First Search
Medium▶ Mock
796.Rotate String
StringString Matching
Easy▶ Mock
2034.Stock Price Fluctuation
Hash TableDesignHeap
Medium▶ Mock
1802.Maximum Value at a Given Index in a Bounded Array
MathBinary SearchGreedy
Medium▶ Mock
3484.Design Spreadsheet
ArrayHash TableString
Medium▶ Mock
631.Design Excel Sum Formula
ArrayHash TableString
Hard▶ Mock
900.RLE Iterator
ArrayDesignCounting
Medium▶ Mock
3043.Find the Length of the Longest Common Prefix
ArrayHash TableString
Medium▶ Mock
Web Crawler Multithreaded
Depth-First SearchBreadth-First SearchConcurrency
Medium▶ Mock
2062.Count Vowel Substrings of a String
Hash TableString
Easy▶ Mock
16.3Sum Closest
ArrayTwo PointersSorting
Medium▶ Mock
18.4Sum
ArrayTwo PointersSorting
Medium▶ Mock
870.Advantage Shuffle
ArrayTwo PointersGreedy
Medium▶ Mock
432.All O'one Data Structure
Hash TableLinked ListDesign
Hard▶ Mock
797.All Paths From Source to Target
BacktrackingDepth-First SearchBreadth-First Search
Medium▶ Mock
1138.Alphabet Board Path
Hash TableString
Medium▶ Mock
2385.Amount of Time for Binary Tree to Be Infected
Hash TableTreeDepth-First Search
Medium▶ Mock
1344.Angle Between Hands of a Clock
Math
Medium▶ Mock
227.Basic Calculator II
MathStringStack
Medium▶ Mock
526.Beautiful Arrangement
ArrayDynamic ProgrammingBacktracking
Medium▶ Mock
1966.Binary Searchable Numbers in an Unsorted Array
ArrayBinary SearchStack
Medium▶ Mock
94.Binary Tree Inorder Traversal
StackTreeDepth-First Search
Easy▶ Mock
144.Binary Tree Preorder Traversal
StackTreeDepth-First Search
Easy▶ Mock
314.Binary Tree Vertical Order Traversal
Hash TableTreeDepth-First Search
Medium▶ Mock
1739.Building Boxes
MathBinary SearchGreedy
Hard▶ Mock
815.Bus Routes
ArrayHash TableBreadth-First Search
Hard▶ Mock
Cache With Time Limit
Medium▶ Mock
605.Can Place Flowers
ArrayGreedy
Easy▶ Mock
1011.Capacity To Ship Packages Within D Days
ArrayBinary Search
Medium▶ Mock
1752.Check if Array Is Sorted and Rotated
Array
Easy▶ Mock
1386.Cinema Seat Allocation
ArrayHash TableGreedy
Medium▶ Mock
Combine Two Tables
Database
Easy▶ Mock
829.Consecutive Numbers Sum
MathEnumeration
Hard▶ Mock
427.Construct Quad Tree
ArrayDivide and ConquerTree
Medium▶ Mock
3875.Construct Uniform Parity Array I
ArrayMath
Easy▶ Mock
220.Contains Duplicate III
ArraySliding WindowSorting
Hard▶ Mock
2276.Count Integers in Intervals
DesignSegment TreeOrdered Set
Hard▶ Mock
3067.Count Pairs of Connectable Servers in a Weighted Tree Network
ArrayTreeDepth-First Search
Medium▶ Mock
2484.Count Different Palindromic Subsequences
StringDynamic Programming
Hard▶ Mock
2791.Count Paths That Can Form a Palindrome in a Tree
Hash TableBit ManipulationTree
Hard▶ Mock
2444.Count Subarrays With Fixed Bounds
ArrayQueueSliding Window
Hard▶ Mock
2954.Count the Number of Infection Sequences
ArrayMathCombinatorics
Hard▶ Mock
2559.Count Vowel Strings in Ranges
ArrayStringPrefix Sum
Medium▶ Mock
Create Hello World Function
Easy▶ Mock
740.Delete and Earn
ArrayHash TableDynamic Programming
Medium▶ Mock
2353.Design a Food Rating System
ArrayHash TableString
Medium▶ Mock
2296.Design a Text Editor
Linked ListStringStack
Hard▶ Mock
588.Design In-Memory File System
Hash TableStringDesign
Hard▶ Mock
3829.Design Ride Sharing System
Hash TableDesignQueue
Medium▶ Mock
353.Design Snake Game
ArrayHash TableDesign
Medium▶ Mock
3408.Design Task Manager
Hash TableDesignHeap
Medium▶ Mock
348.Design Tic-Tac-Toe
ArrayHash TableDesign
Medium▶ Mock
1396.Design Underground System
Hash TableStringDesign
Medium▶ Mock
2204.Distance to a Cycle in Undirected Graph
Depth-First SearchBreadth-First SearchGraph
Hard▶ Mock
115.Distinct Subsequences
StringDynamic Programming
Hard▶ Mock
72.Edit Distance
StringDynamic Programming
Medium▶ Mock
271.Encode and Decode Strings
ArrayStringDesign
Medium▶ Mock
636.Exclusive Time of Functions
ArrayStack
Medium▶ Mock
509.Fibonacci Number
MathDynamic ProgrammingRecursion
Easy▶ Mock
1475.Final Prices With a Special Discount in a Shop
ArrayStackMonotonic Stack
Easy▶ Mock
55.Jump Game
ArrayDynamic ProgrammingGreedy
Medium▶ Mock
141.Linked List Cycle
Hash TableLinked ListTwo Pointers
Easy▶ Mock
337.House Robber III
Dynamic ProgrammingTreeDepth-First Search
Medium▶ Mock
32.Longest Valid Parentheses
StringDynamic ProgrammingStack
Hard▶ Mock
153.Find Minimum in Rotated Sorted Array
ArrayBinary Search
Medium▶ Mock
162.Find Peak Element
ArrayBinary Search
Medium▶ Mock
57.Insert Interval
Array
Medium▶ Mock
986.Interval List Intersections
ArrayTwo PointersSweep Line
Medium▶ Mock
785.Is Graph Bipartite?
Depth-First SearchBreadth-First SearchUnion Find
Medium▶ Mock
84.Largest Rectangle in Histogram
ArrayStackMonotonic Stack
Hard▶ Mock
289.Game of Life
ArrayMatrixSimulation
Medium▶ Mock
287.Find the Duplicate Number
ArrayTwo PointersBinary Search
Medium▶ Mock
802.Find Eventual Safe States
Depth-First SearchBreadth-First SearchGraph
Medium▶ Mock
179.Largest Number
ArrayStringGreedy
Medium▶ Mock
213.House Robber II
ArrayDynamic Programming
Medium▶ Mock
28.Find the Index of the First Occurrence in a String
Two PointersStringString Matching
Easy▶ Mock
1048.Longest String Chain
ArrayHash TableTwo Pointers
Medium▶ Mock
845.Longest Mountain in Array
ArrayTwo PointersDynamic Programming
Medium▶ Mock
658.Find K Closest Elements
ArrayTwo PointersBinary Search
Medium▶ Mock
2933.High-Access Employees
ArrayHash TableString
Medium▶ Mock
609.Find Duplicate File in System
ArrayHash TableString
Medium▶ Mock
2812.Find the Safest Path in a Grid
ArrayBinary SearchBreadth-First Search
Medium▶ Mock
1438.Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit
ArrayQueueSliding Window
Medium▶ Mock
2373.Largest Local Values in a Matrix
ArrayMatrix
Easy▶ Mock
564.Find the Closest Palindrome
MathString
Hard▶ Mock
1004.Max Consecutive Ones III
ArrayBinary SearchSliding Window
Medium▶ Mock
643.Maximum Average Subarray I
ArraySliding Window
Easy▶ Mock
1768.Merge Strings Alternately
Two PointersString
Easy▶ Mock
1200.Minimum Absolute Difference
ArraySorting
Easy▶ Mock
983.Minimum Cost For Tickets
ArrayDynamic Programming
Medium▶ Mock
670.Maximum Swap
MathGreedy
Medium▶ Mock
628.Maximum Product of Three Numbers
ArrayMathSorting
Easy▶ Mock
3914.Minimum Operations to Make Array Non Decreasing
ArrayGreedy
Medium▶ Mock
1249.Minimum Remove to Make Valid Parentheses
StringStack
Medium▶ Mock
209.Minimum Size Subarray Sum
ArrayBinary SearchSliding Window
Medium▶ Mock
2461.Maximum Sum of Distinct Subarrays With Length K
ArrayHash TableSliding Window
Medium▶ Mock
3090.Maximum Length Substring With Two Occurrences
Hash TableStringSliding Window
Easy▶ Mock
849.Maximize Distance to Closest Person
Array
Medium▶ Mock
131.Palindrome Partitioning
StringDynamic ProgrammingBacktracking
Medium▶ Mock
1136.Parallel Courses
GraphTopological SortDirected Acyclic Graph
Medium▶ Mock
46.Permutations
ArrayBacktracking
Medium▶ Mock
66.Plus One
ArrayMath
Easy▶ Mock
2551.Put Marbles in Bags
ArrayGreedySorting
Hard▶ Mock
1366.Rank Teams by Votes
ArrayHash TableString
Medium▶ Mock
2561.Rearranging Fruits
ArrayHash TableGreedy
Hard▶ Mock
1209.Remove All Adjacent Duplicates in String II
StringStack
Medium▶ Mock
27.Remove Element
ArrayTwo Pointers
Easy▶ Mock
402.Remove K Digits
StringStackGreedy
Medium▶ Mock
767.Reorganize String
Hash TableStringGreedy
Medium▶ Mock
93.Restore IP Addresses
StringBacktracking
Medium▶ Mock
51.N-Queens
ArrayBacktrackingAlgorithm X
Hard▶ Mock
743.Network Delay Time
Depth-First SearchBreadth-First SearchGraph
Medium▶ Mock
547.Number of Provinces
Depth-First SearchBreadth-First SearchUnion Find
Medium▶ Mock
933.Number of Recent Calls
DesignQueueData Stream
Easy▶ Mock
857.Minimum Cost to Hire K Workers
ArrayGreedySorting
Hard▶ Mock
1928.Minimum Cost to Reach Destination in Time
ArrayDynamic ProgrammingGraph
Hard▶ Mock
871.Minimum Number of Refueling Stops
ArrayDynamic ProgrammingGreedy
Hard▶ Mock
827.Making A Large Island
ArrayDepth-First SearchBreadth-First Search
Hard▶ Mock
716.Max Stack
Linked ListStackDesign
Hard▶ Mock
3035.Maximum Palindromes After Operations
ArrayHash TableString
Medium▶ Mock
3893.Maximum Team Size with Overlapping Intervals
ArraySortingUnion Find
Medium▶ Mock
3634.Minimum Removals to Balance Array
ArrayBinary SearchSliding Window
Medium▶ Mock
2366.Minimum Replacements to Sort the Array
ArrayMathGreedy
Hard▶ Mock
3413.Maximum Coins From K Consecutive Bags
ArrayBinary SearchGreedy
Medium▶ Mock
3953.Maximum Score with Co-Prime Element
ArrayHash TableMath
Hard▶ Mock
3387.Maximize Amount After Two Days of Conversions
ArrayStringDepth-First Search
Medium▶ Mock
3367.Maximize Sum of Weights after Edge Removals
Dynamic ProgrammingTreeDepth-First Search
Hard▶ Mock
2251.Number of Flowers in Full Bloom
ArrayHash TableBinary Search
Hard▶ Mock
305.Number of Islands II
ArrayHash TableUnion Find
Hard▶ Mock
3649.Number of Perfect Pairs
ArrayMathTwo Pointers
Medium▶ Mock
1944.Number of Visible People in a Queue
ArrayStackMonotonic Stack
Hard▶ Mock
1639.Number of Ways to Form a Target String Given a Dictionary
ArrayStringDynamic Programming
Hard▶ Mock
1915.Number of Wonderful Substrings
Hash TableStringBit Manipulation
Medium▶ Mock
465.Optimal Account Balancing
ArrayDynamic ProgrammingBacktracking
Hard▶ Mock
1931.Painting a Grid With Three Different Colors
Dynamic ProgrammingGraph Coloring
Hard▶ Mock
74.Search a 2D Matrix
ArrayBinary SearchMatrix
Medium▶ Mock
35.Search Insert Position
ArrayBinary Search
Easy▶ Mock
73.Set Matrix Zeroes
ArrayHash TableMatrix
Medium▶ Mock
136.Single Number
ArrayBit Manipulation
Easy▶ Mock
912.Sort an Array
ArrayDivide and ConquerSorting
Medium▶ Mock
69.Sqrt(x)
MathBinary SearchNewton's Method
Easy▶ Mock
36.Valid Sudoku
ArrayHash TableMatrix
Medium▶ Mock
678.Valid Parenthesis String
StringDynamic ProgrammingStack
Medium▶ Mock
Rising Temperature
Database
Easy▶ Mock
228.Summary Ranges
Array
Easy▶ Mock
645.Set Mismatch
ArrayHash TableBit Manipulation
Easy▶ Mock
3345.Smallest Divisible Digit Product I
MathEnumeration
Easy▶ Mock
3718.Smallest Missing Multiple of K
ArrayHash Table
Easy▶ Mock
443.String Compression
Two PointersString
Medium▶ Mock
713.Subarray Product Less Than K
ArrayBinary SearchSliding Window
Medium▶ Mock
692.Top K Frequent Words
ArrayHash TableString
Medium▶ Mock
71.Simplify Path
StringStack
Medium▶ Mock
384.Shuffle an Array
ArrayMathDesign
Medium▶ Mock
1010.Pairs of Songs With Total Durations Divisible by 60
ArrayHash TableCounting
Medium▶ Mock
Nth Highest Salary
Database
Medium▶ Mock
Second Highest Salary
Database
Medium▶ Mock
737.Sentence Similarity II
ArrayHash TableString
Medium▶ Mock
1101.The Earliest Moment When Everyone Become Friends
ArrayUnion FindSorting
Medium▶ Mock
2039.The Time When the Network Becomes Idle
ArrayBreadth-First SearchGraph
Medium▶ Mock
2380.Time Needed to Rearrange a Binary String
StringDynamic ProgrammingSimulation
Medium▶ Mock
1970.Last Day Where You Can Still Cross
ArrayBinary SearchDepth-First Search
Hard▶ Mock
1428.Leftmost Column with at Least a One
ArrayBinary SearchMatrix
Medium▶ Mock
2213.Longest Substring of One Repeating Character
ArrayStringSegment Tree
Hard▶ Mock
1644.Lowest Common Ancestor of a Binary Tree II
TreeDepth-First SearchBinary Tree
Medium▶ Mock
1650.Lowest Common Ancestor of a Binary Tree III
Hash TableTwo PointersTree
Medium▶ Mock
1676.Lowest Common Ancestor of a Binary Tree IV
Hash TableTreeDepth-First Search
Medium▶ Mock
2948.Make Lexicographically Smallest Array by Swapping Elements
ArrayUnion FindSorting
Medium▶ Mock
332.Reconstruct Itinerary
ArrayStringDepth-First Search
Hard▶ Mock
25.Reverse Nodes in k-Group
Linked ListRecursion
Hard▶ Mock
354.Russian Doll Envelopes
ArrayBinary SearchDynamic Programming
Hard▶ Mock
428.Serialize and Deserialize N-ary Tree
StringTreeDepth-First Search
Hard▶ Mock
1293.Shortest Path in a Grid with Obstacles Elimination
ArrayBreadth-First SearchMatrix
Hard▶ Mock
2096.Step-By-Step Directions From a Binary Tree Node to Another
StringTreeDepth-First Search
Medium▶ Mock
664.Strange Printer
StringDynamic Programming
Hard▶ Mock
2718.Sum of Matrix After Queries
ArrayHash Table
Medium▶ Mock
1258.Synonymous Sentences
ArrayHash TableString
Medium▶ Mock
980.Unique Paths III
ArrayBacktrackingBit Manipulation
Hard▶ Mock
2434.Using a Robot to Print the Lexicographically Smallest String
Hash TableStringStack
Medium▶ Mock
987.Vertical Order Traversal of a Binary Tree
Hash TableTreeDepth-First Search
Hard▶ Mock
1236.Web Crawler
StringDepth-First SearchBreadth-First Search
Medium▶ Mock
140.Word Break II
ArrayHash TableString
Hard▶ Mock
Valid Anagram
Hash TableStringSorting
Easy▶ Mock
Missing Number
ArrayHash TableMath
Easy▶ Mock
Happy Number
Hash TableMathTwo Pointers
Easy+1▶ Mock
Design Add and Search Words Data Structure
StringDepth-First SearchDesign
Medium▶ Mock
Populating Next Right Pointers in Each Node
Linked ListTreeDepth-First Search
Medium+1▶ Mock
Word Search II
ArrayStringBacktracking
Hard+1▶ Mock
43.Multiply Strings
MathStringSimulation
Medium▶ Mock
64.Minimum Path Sum
ArrayDynamic ProgrammingMatrix
Medium▶ Mock
65.Valid Number
String
Hard▶ Mock
110.Balanced Binary Tree
TreeDepth-First SearchBinary Tree
Easy▶ Mock
118.Pascal's Triangle
ArrayDynamic Programming
Easy▶ Mock
149.Max Points on a Line
ArrayHash TableMath
Hard▶ Mock
166.Fraction to Recurring Decimal
Hash TableMathString
Medium▶ Mock
199.Binary Tree Right Side View
TreeDepth-First SearchBreadth-First Search
Medium▶ Mock
205.Isomorphic Strings
Hash TableString
Easy▶ Mock
240.Search a 2D Matrix II
ArrayBinary SearchDivide and Conquer
Medium▶ Mock
243.Shortest Word Distance
ArrayString
Easy▶ Mock
244.Shortest Word Distance II
ArrayHash TableTwo Pointers
Medium▶ Mock
257.Binary Tree Paths
StringBacktrackingTree
Easy▶ Mock
272.Closest Binary Search Tree Value II
Two PointersStackTree
Hard▶ Mock
282.Expression Add Operators
MathStringBacktracking
Hard▶ Mock
319.Bulb Switcher
MathBrainteaser
Medium▶ Mock
340.Longest Substring with At Most K Distinct Characters
Hash TableStringSliding Window
Medium▶ Mock
364.Nested List Weight Sum II
StackDepth-First SearchBreadth-First Search
Medium▶ Mock
381.Insert Delete GetRandom O(1) - Duplicates allowed
ArrayHash TableMath
Hard▶ Mock
383.Ransom Note
Hash TableStringCounting
Easy▶ Mock
387.First Unique Character in a String
Hash TableStringQueue
Easy▶ Mock
394.Decode String
StringStackRecursion
Medium▶ Mock
437.Path Sum III
TreeDepth-First SearchBinary Tree
Medium▶ Mock
445.Add Two Numbers II
Linked ListMathStack
Medium▶ Mock
475.Heaters
ArrayTwo PointersBinary Search
Medium▶ Mock
494.Target Sum
ArrayDynamic ProgrammingBacktracking
Medium▶ Mock
496.Next Greater Element I
ArrayHash TableStack
Easy▶ Mock
528.Random Pick with Weight
ArrayMathBinary Search
Medium▶ Mock
543.Diameter of Binary Tree
TreeDepth-First SearchBinary Tree
Easy▶ Mock
622.Design Circular Queue
ArrayLinked ListDesign
Medium▶ Mock
642.Design Search Autocomplete System
StringDepth-First SearchDesign
Hard▶ Mock
657.Robot Return to Origin
StringSimulation
Easy▶ Mock
694.Number of Distinct Islands
Hash TableDepth-First SearchBreadth-First Search
Medium▶ Mock
696.Count Binary Substrings
Two PointersString
Easy▶ Mock
701.Insert into a Binary Search Tree
TreeBinary Search TreeBinary Tree
Medium▶ Mock
706.Design HashMap
ArrayHash TableLinked List
Easy▶ Mock
723.Candy Crush
ArrayTwo PointersMatrix
Medium▶ Mock
749.Contain Virus
ArrayDepth-First SearchBreadth-First Search
Hard▶ Mock
773.Sliding Puzzle
ArrayDynamic ProgrammingBacktracking
Hard▶ Mock
779.K-th Symbol in Grammar
MathBit ManipulationRecursion
Medium▶ Mock
787.Cheapest Flights Within K Stops
Dynamic ProgrammingDepth-First SearchBreadth-First Search
Medium▶ Mock
790.Domino and Tromino Tiling
Dynamic Programming
Medium▶ Mock
838.Push Dominoes
Two PointersStringDynamic Programming
Medium▶ Mock
851.Loud and Rich
ArrayDepth-First SearchGraph
Medium▶ Mock
853.Car Fleet
ArrayStackSorting
Medium▶ Mock
886.Possible Bipartition
Depth-First SearchBreadth-First SearchUnion Find
Medium▶ Mock
928.Minimize Malware Spread II
ArrayHash TableDepth-First Search
Hard▶ Mock
968.Binary Tree Cameras
Dynamic ProgrammingTreeDepth-First Search
Hard▶ Mock
973.K Closest Points to Origin
ArrayMathDivide and Conquer
Medium▶ Mock
974.Subarray Sums Divisible by K
ArrayHash TablePrefix Sum
Medium▶ Mock
1029.Two City Scheduling
ArrayGreedySorting
Medium▶ Mock
1043.Partition Array for Maximum Sum
ArrayDynamic Programming
Medium▶ Mock
1055.Shortest Way to Form String
Two PointersStringBinary Search
Medium▶ Mock
1086.High Five
ArrayHash TableSorting
Easy▶ Mock
1087.Brace Expansion
StringBacktrackingBreadth-First Search
Medium▶ Mock
1125.Smallest Sufficient Team
ArrayDynamic ProgrammingBit Manipulation
Hard▶ Mock
1145.Binary Tree Coloring Game
TreeDepth-First SearchBinary Tree
Medium▶ Mock
1202.Smallest String With Swaps
ArrayHash TableString
Medium▶ Mock
1235.Maximum Profit in Job Scheduling
ArrayBinary SearchDynamic Programming
Hard▶ Mock
1244.Design A Leaderboard
Hash TableDesignSorting
Medium▶ Mock
1248.Count Number of Nice Subarrays
ArrayHash TableMath
Medium▶ Mock
1297.Maximum Number of Occurrences of a Substring
Hash TableStringSliding Window
Medium▶ Mock
1298.Maximum Candies You Can Get from Boxes
ArrayBreadth-First SearchGraph
Hard▶ Mock
1347.Minimum Number of Steps to Make Two Strings Anagram
Hash TableStringCounting
Medium▶ Mock
1352.Product of the Last K Numbers
ArrayMathDesign
Medium▶ Mock
1353.Maximum Number of Events That Can Be Attended
ArrayGreedySorting
Medium▶ Mock
1434.Number of Ways to Wear Different Hats to Each Other
ArrayDynamic ProgrammingBit Manipulation
Hard▶ Mock
1482.Minimum Number of Days to Make m Bouquets
ArrayBinary Search
Medium▶ Mock
1535.Find the Winner of an Array Game
ArraySimulation
Medium▶ Mock
1564.Put Boxes Into the Warehouse I
ArrayGreedySorting
Medium▶ Mock
1600.Throne Inheritance
Hash TableTreeDepth-First Search
Medium▶ Mock
1610.Maximum Number of Visible Points
ArrayMathGeometry
Hard▶ Mock
1642.Furthest Building You Can Reach
ArrayGreedyHeap
Medium▶ Mock
1648.Sell Diminishing-Valued Colored Balls
ArrayMathBinary Search
Medium▶ Mock
1710.Maximum Units on a Truck
ArrayGreedySorting
Easy▶ Mock
1751.Maximum Number of Events That Can Be Attended II
ArrayBinary SearchDynamic Programming
Hard▶ Mock
1762.Buildings With an Ocean View
ArrayStackMonotonic Stack
Medium▶ Mock
1823.Find the Winner of the Circular Game
ArrayMathRecursion
Medium▶ Mock
1828.Queries on Number of Points Inside a Circle
ArrayMathGeometry
Medium▶ Mock
1834.Single-Threaded CPU
ArraySortingHeap
Medium▶ Mock
1963.Minimum Number of Swaps to Make the String Balanced
Two PointersStringStack
Medium▶ Mock
2043.Simple Bank System
ArrayHash TableDesign
Medium▶ Mock
2050.Parallel Courses III
ArrayDynamic ProgrammingGraph
Hard▶ Mock
2097.Valid Arrangement of Pairs
Depth-First SearchGraphEulerian Circuit
Hard▶ Mock
2101.Detonate the Maximum Bombs
ArrayMathDepth-First Search
Medium▶ Mock
2171.Removing Minimum Number of Magic Beans
ArrayGreedySorting
Medium▶ Mock
2232.Minimize Result by Adding Parentheses to Expression
StringEnumeration
Medium▶ Mock
2237.Count Positions on Street With Required Brightness
ArrayPrefix Sum
Medium▶ Mock
2243.Calculate Digit Sum of a String
StringSimulation
Easy▶ Mock
2265.Count Nodes Equal to Average of Subtree
TreeDepth-First SearchBinary Tree
Medium▶ Mock
2303.Calculate Amount Paid in Taxes
ArraySimulation
Easy▶ Mock
2360.Longest Cycle in a Graph
Depth-First SearchBreadth-First SearchGraph
Hard▶ Mock
2439.Minimize Maximum of Array
ArrayBinary SearchDynamic Programming
Medium▶ Mock
2466.Count Ways To Build Good Strings
Dynamic Programming
Medium▶ Mock
2491.Divide Players Into Teams of Equal Skill
ArrayHash TableTwo Pointers
Medium▶ Mock
2672.Number of Adjacent Elements With the Same Color
Array
Medium▶ Mock
2680.Maximum OR
ArrayGreedyBit Manipulation
Medium▶ Mock
2895.Minimum Processing Time
ArrayGreedySorting
Medium▶ Mock
2914.Minimum Number of Changes to Make Binary String Beautiful
String
Medium▶ Mock
2964.Number of Divisible Triplet Sums
ArrayHash Table
Medium▶ Mock
3076.Shortest Uncommon Substring in an Array
ArrayHash TableString
Medium▶ Mock
3078.Match Alphanumerical Pattern in Matrix I
ArrayHash TableString
Medium▶ Mock
3092.Most Frequent IDs
ArrayHash TableHeap
Medium▶ Mock
3161.Block Placement Queries
ArrayBinary SearchBinary Indexed Tree
Hard▶ Mock
3208.Alternating Groups II
ArraySliding Window
Medium▶ Mock
3919.Minimum Cost to Move Between Indices
ArrayPrefix Sum
Medium▶ Mock

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