C++ / Data structures & algorithms
Explore the code. Understand the reasoning. A source archive of contest solutions and core algorithms. Search a problem, choose a contest collection, or explore by topic. Choose a solution, then switch between its code and the accompanying explanation of the approach, examples, and complexity. Write-ups load directly from the repository where available.
Start with a technique Dynamic programming → Disjoint sets → Two pointers → 66 explanations
All topics Data structures Dynamic programming Graphs Greedy Mathematics Search Shortest paths
PROBLEM INDEX A little order? 79 files 1. Two Sum LeetCode 104. Maximum Depth of Binary Tree LeetCode 11. Container With Most Water LeetCode 142. Linked List Cycle II LeetCode 1721. Swapping Nodes in a Linked List LeetCode 19. Remove Nth Node From End of List LeetCode 2. Add Two Numbers LeetCode 206. Reverse Linked List LeetCode 2116. Check if a Parentheses String Can Be Valid LeetCode 22. Generate Parentheses LeetCode 230. Kth Smallest Element in a BST LeetCode 234. Palindrome Linked List LeetCode 24. Swap Nodes in Pairs LeetCode 287. Find the Duplicate Number LeetCode 33. Search in Rotated Sorted Array LeetCode 347. Top K Frequent Elements LeetCode 42. Trapping Rain Water LeetCode 451. Sort Characters By Frequency LeetCode 495. Teemo Attacking LeetCode 5. Longest Palindromic Substring LeetCode 56. Merge Intervals LeetCode 57. Insert Interval LeetCode 61. Rotate List LeetCode 62. Unique Paths LeetCode 63. Unique Paths II LeetCode 64. Minimum Path Sum LeetCode 647. Palindromic Substrings LeetCode 74. Search a 2D Matrix LeetCode 81. Search in Rotated Sorted Array II LeetCode 88. Merge Sorted Array LeetCode 9. Palindrome Number LeetCode 92. Reverse Linked List II LeetCode 94. Binary Tree Inorder Traversal LeetCode 96. Unique Binary Search Trees LeetCode 977. Squares of a Sorted Array LeetCode 98. Validate Binary Search Tree LeetCode 980. Unique Paths III LeetCode 99. Recover Binary Search Tree LeetCode A Noisy Class Practice / Graphs CCC '00 S2 - Babbling Brooks CCC CCC '00 S4 - Golf CCC / Dynamic programming CCC '03 S3 - Floor Plan CCC / Graphs · Search CCC '05 J5 - Bananas CCC CCC '07 J4 - Anagram Checker CCC CCC '07 J5 - Keep on Truckin' CCC / Dynamic programming CCC '07 S4 - Waterpark CCC CCC '09 S3 - Degrees Of Separation CCC / Graphs · Search CCC '10 J5 - Knight Hop CCC / Graphs · Search CCC '11 J4 - Boring Business CCC CCC '11 J5 - Unfriend CCC CCC '12 S5 - Mouse Journey CCC / Dynamic programming CCC '13 S2 - Bridge Transport CCC CCC '14 S2 - Assigning Partners CCC CCC '14 S3 - The Geneva Confection CCC / Data structures CCC '15 S3 - Gates CCC / Data structures · Greedy CCC '16 S2 - Tandem Bicycle CCC / Greedy CCC '18 J5 - Choose your own path CCC / Graphs · Search CCC '20 S2 - Escape Room CCC / Graphs · Search CCC '96 S4 - When in Rome CCC CCCHK '15 J3 - Queens can't attack me! CCCHK CCO '10 P4 - Computer Purchase Return CCO Coin Change Practice / Dynamic programming CTU Open Contest 2018 - Horsemeet CTU / Mathematics Disjoint Set Test Practice / Data structures · Graphs DMOPC '16 Contest 1 P3 - Shoe Shopping DMOPC / Dynamic programming DMPG '15 B4 - Maximum Product DMPG DWITE '08 R4 #1 - Four player Pong with no players DWITE Facebook Hacker Cup '15 Round 1 P1 - Homework Facebook Hacker Cup / Mathematics Fibonacci Sequence Practice / Mathematics IOI '09 P3 - POI IOI IOI '09 P5 - Garage IOI IOI '94 P1 - The Triangle IOI / Dynamic programming Longest Common Subsequence Practice / Dynamic programming Longest Increasing Subsequence Practice / Dynamic programming Postfix Notation Practice / Data structures Sudoku Challenge Practice / Search Ternary Search Tree Practice / Data structures TLE '17 Contest 3 P3 - Fax's Thanksgiving Dish TLE Traffic Lights Practice / Graphs · Shortest paths
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Coin Change.cpp Practice Dynamic programming 1.3 KB Copy source
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Topic labels cover implementations reviewed on October 6, 2026. Untagged files remain searchable by name and collection. Inspired by the repository’s note: try the problem yourself before reading a solution.