DSA Patterns Sheet

The DSA Patterns Sheet organises 410 data structures and algorithms problems by the technique that solves them, not by the data structure they happen to mention: 16 pattern families broken into 100 subpatterns, each with the problems that drill it.

A pattern is a reusable line of reasoning. Recognising that a question is a sliding window question is most of the work; the code that follows is short and nearly always the same shape. That is why a candidate who has solved two hundred problems at random can still be beaten by one who has worked through 16 patterns deliberately — the second one recognises the unseen question, and the first only recognises the seen one.

How to use the sheet

Take one pattern at a time. Read the pattern page, solve the easiest problem under it without help, then the medium ones until the setup stops feeling like a decision. Mark each row done, bookmark the ones you fumbled, and come back to the bookmarks a week later rather than to the whole list. Every row links to the problem in the browser editor, to its editorial, and to an AI mock interview on that specific pattern; code runs in 6 languages — Python, C++, Java, JavaScript, Go, C#.

Progress is stored against your account, so the sheet doubles as the record of what you have covered. You can filter it by company to see how a target company's evidenced questions land across the same patterns.

The 16 pattern families

• Array & Matrix Manipulation Patterns10 subpatterns — Merge Sorted Array (In-place from End), Spiral Traversal, Set Matrix Zeroes (In-place Marking), Hashing - Frequency Map / Counting, Prefix Sum - Subarray Sum / Range Query, Product Except Self (Prefix/Suffix Products), Plus One (Handling Carry), Array - Cyclic Sort, Hashing - Previously Seen / Existence Check, In-place Rotation
• Linked List Manipulation Patterns5 subpatterns — Reordering / Partitioning, In-place Reversal, Merging Two Sorted Lists, Addition of Numbers, Intersection Detection
• Two Pointers Pattern7 subpatterns — Fast & Slow (Cycle Detection), Converging (Sorted Array Target Sum), Expanding From Center (Palindromes), String Comparison with Backspaces, String Reversal, In-place Array Modification, Fixed Separation (Nth Node from End)
• Sliding Window Pattern4 subpatterns — Fixed Size (Subarray Calculation), Monotonic Queue for Max/Min, Variable Size (Condition-Based), Character Frequency Matching
• Binary Search Patterns5 subpatterns — On Sorted Array/List, Find First/Last Occurrence, Find Min/Max in Rotated Sorted Array, Median and Kth of Two Sorted Arrays, On Answer / Condition Function
• Stack Patterns6 subpatterns — Valid Parentheses Matching, Monotonic Stack, Largest Rectangle in Histogram, Stack - Min Stack Design, Simulation / Backtracking Helper, Expression Evaluation (RPN/Infix)
• String Manipulation Patterns7 subpatterns — Repeated Substring Pattern Detection, Naive / KMP / Rabin-Karp, Palindrome Check (Two Pointers / Reverse), Integer and Roman Conversion, Multiply Strings (Manual Simulation), String to Integer (atoi), Anagram Check (Frequency Count/Sort)
• Heap and Priority Queue Patterns4 subpatterns — K-way Merge, Top K Elements (Selection/Frequency), Scheduling / Minimum Cost (Greedy with Priority Queue), Two Heaps for Median Finding
• Tree Traversal Patterns - DFS and BFS6 subpatterns — Recursive Preorder Traversal, Recursive Inorder Traversal, Level Order Traversal, Recursive Postorder Traversal, Serialization and Deserialization, Lowest Common Ancestor (LCA) Finding
• Graph Traversal Patterns - DFS and BFS12 subpatterns — Graph DFS - Connected Components / Island Counting, Graph BFS - Connected Components / Island Counting, Graph BFS - Topological Sort (Kahn's Algorithm), Graph DFS - Cycle Detection (Directed Graph), Shortest Path (Bellman-Ford / BFS+K), Shortest Path (Dijkstra's Algorithm), Deep Copy / Cloning, Bidirectional BFS (BFS optimization for known source & target), Bridges & Articulation Points (Tarjan low-link), Union-Find (Disjoint Set Union - DSU), Minimum Spanning Tree (Kruskal / Prim / DSU + heap), Strongly Connected Components (Kosaraju / Tarjan)
• Greedy Algorithm Patterns7 subpatterns — Jump Game Reachability/Minimization, Sorting Based, Task Scheduling (Frequency Based), Interval Merging/Scheduling, Line Sweep, Gas Station Circuit, Buy/Sell Stock
• Backtracking Patterns7 subpatterns — Word Search / Path Finding in Grid, N-Queens / Constraint Satisfaction, Permutations, Palindrome Partitioning, Combination Sum, Subsets (Include/Exclude), Parentheses Generation
• Dynamic Programming Patterns12 subpatterns — 2D Array (Edit Distance / Levenshtein Distance), 1D Array (Kadane's Algorithm for Max/Min Subarray), Interval DP, 2D Array (Unique Paths on Grid), 1D Array (Fibonacci Style), 1D Array (0/1 Knapsack Subset Sum Style), 2D Array (Longest Common Subsequence - LCS), Catalan Numbers, 1D Array (Word Break Style), Stock problems, 1D Array (Coin Change / Unbounded Knapsack Style), Longest Increasing Subsequence (LIS)
• Bit Manipulation Patterns4 subpatterns — Bitwise Operations - Power of Two/Four Check, Bitwise XOR - Finding Single/Missing Number, Bitwise DP - Counting Bits Optimization, Bitwise AND - Counting Set Bits (Hamming Weight)
• Design Patterns - Data Structure Implementation2 subpatterns — Tries, Design (General/Specific)
• Segment Tree and Fenwick Tree Patterns2 subpatterns — Fenwick Tree (BIT) - Prefix Queries / Inversions, Segment Tree - Range Sum with Point Update

All 404 problems by pattern