codedive

Visual algorithm learning — step through code, watch data structures animate.

145 problems·18 collections·26 easy·99 medium·20 hard
01

Arrays & Hashing

3E9M
217Contains DuplicateE242Valid AnagramE2Two SumE3636. Valid SudokuM4949. Group AnagramsM347Top K Frequent ElementsM238Product of Array Except SelfM271Encode and Decode StringsM128Longest Consecutive SequenceM73Set Matrix ZeroesM5454. Spiral MatrixM4848. Rotate ImageM
02

Two Pointers

1E3M1H
1Valid PalindromeE167Two Sum II - Input Array Is SortedM153SumM11Container With Most WaterM4242. Trapping Rain WaterH
03

Sliding Window

3M2H
3Longest Substring Without Repeating CharactersM424Longest Repeating Character ReplacementM567567. Permutation in StringM76Minimum Window SubstringH239Sliding Window MaximumH
04

Stack

1E5M1H
2020. Valid ParenthesesE155Min StackM150Evaluate Reverse Polish NotationM2222. Generate ParenthesesM739Daily TemperaturesM853Car FleetM84Largest Rectangle in HistogramH
05

Binary Search

1E5M1H
704Binary SearchE74Search a 2D MatrixM875Koko Eating BananasM153Find Minimum in Rotated Sorted ArrayM3333. Search in Rotated Sorted ArrayM981Time Based Key-Value StoreM5Median of Two Sorted ArraysH
06

Linked List

3E6M2H
206Reverse Linked ListE2121. Merge Two Sorted ListsE141Linked List CycleE1919. Remove Nth Node From End of ListM138Copy List with Random PointerM4Add Two NumbersM287Find the Duplicate NumberM146LRU CacheM143Reorder ListM2525. Reverse Nodes in k-GroupH2323. Merge k Sorted ListsH
07

Trees

6E7M1H
226Invert Binary TreeE104Maximum Depth of Binary TreeE543543. Diameter of Binary TreeE100Same TreeE572Subtree of Another TreeE110Balanced Binary TreeE102Binary Tree Level Order TraversalM199Binary Tree Right Side ViewM1448Count Good Nodes in Binary TreeM98Validate Binary Search TreeM230Kth Smallest Element in a BSTM235Lowest Common Ancestor of a Binary Search TreeM105Construct Binary Tree from Preorder and Inorder TraversalM124Binary Tree Maximum Path SumH
08

Tries

2M1H
208Implement Trie (Prefix Tree)M211Design Add and Search Words Data StructureM212Word Search IIH
09

Heap / Priority Queue

2E4M1H
1046Last Stone WeightE215Kth Largest Element in an ArrayM973K Closest Points to OriginM621Task SchedulerM703Kth Largest Element in a StreamE355Design TwitterM295Find Median from Data StreamH
10

Backtracking

7M1H
78SubsetsM3939. Combination SumM4040. Combination Sum IIM4646. PermutationsM1717. Letter Combinations of a Phone NumberM79Word SearchM131Palindrome PartitioningM5151. N-QueensH
11

Graphs

11M1H
200Number of IslandsM695Max Area of IslandM133Clone GraphM286Walls and GatesM994Rotting OrangesM417Pacific Atlantic Water FlowM130Surrounded RegionsM261Graph Valid TreeM207Course ScheduleM210Course Schedule IIM684Redundant ConnectionM127Word LadderH
12

Advanced Graphs

3M3H
743Network Delay TimeM1584Min Cost to Connect All PointsM787Cheapest Flights Within K StopsM778Swim in Rising WaterH332Reconstruct ItineraryH269Alien DictionaryH
13

1-D Dynamic Programming

2E11M
746Min Cost Climbing StairsE121Best Time to Buy and Sell StockE198House RobberM213House Robber IIM5Longest Palindromic SubstringM647Palindromic SubstringsM91Decode WaysM322Coin ChangeM152Maximum Product SubarrayM139Word BreakM416Partition Equal Subset SumM494Target SumM300Longest Increasing SubsequenceM
14

2-D Dynamic Programming

5M3H
62Unique PathsM1143Longest Common SubsequenceM6Coin Change IIM72Edit DistanceM97Interleaving StringM115Distinct SubsequencesH10Regular Expression MatchingH312Burst BalloonsH
15

Greedy

8M
5353. Maximum SubarrayM5555. Jump GameM4545. Jump Game IIM134Gas StationM846Hand of StraightsM1899Merge Triplets to Form Target TripletM763Partition LabelsM678Valid Parenthesis StringM
16

Intervals

1E3M1H
252Meeting RoomsE5656. Merge IntervalsM253Meeting Rooms IIM435Non-overlapping IntervalsM1851Minimum Interval to Include Each QueryH
17

Math & Bit Manipulation

6E5M
268Missing NumberE136Single NumberE202Happy NumberE191Number of 1 BitsE190Reverse BitsE338Counting BitsE7Reverse IntegerM371Sum of Two IntegersM5050. Pow(x, n)M4343. Multiply StringsM2013Detect SquaresM
18

Other

2M1H
309Stock with CooldownM323Number of Connected ComponentsM329Longest Increasing PathH