DSA — Data Structures & Algorithms
Everything you need to crack coding rounds at Amazon, Google, Meta, PhonePe, Flipkart, and beyond.
🚀 Where to start?
| Your situation | Recommended path | Time needed |
|---|---|---|
| Interview in 1 week | Quick-Fire 50 — the 50 most-asked problems with one-line approaches | 7 days |
| Interview in 1 month | The 75 — covers every pattern, one problem each | 4-5 weeks |
| Deep prep (2 months) | The 150 — full coverage with depth per pattern | 6-8 weeks |
| Don’t know patterns yet | DSA Fundamentals — 12 patterns, complexity analysis, how to approach any problem | 1-2 days |
📋 Curated Problem Lists
Each list has LeetCode links for every problem + a progress tracker (checkboxes save in your browser automatically).
| List | Problems | What it covers | Checkpoint |
|---|---|---|---|
| 📋 Quick-Fire 50 | 50 | Most-frequently asked, one per pattern | Complete in 7-10 days |
| 🎯 The 75 — Interview Sprint | 75 | Every pattern with enough depth to be interview-ready | Complete in 4-5 weeks |
| 📚 The 150 — Complete Prep | 150 | Deep coverage: advanced graphs, 2D DP, bit manipulation | Complete in 6-8 weeks |
🧩 Browse by Pattern
| Pattern | What to recognize | Key problems |
|---|---|---|
| Two Pointers | Sorted array, find pair, shrink from both ends | 3Sum, Container With Most Water, Trapping Rain Water |
| Sliding Window | Contiguous subarray/substring with a constraint | Longest Substring, Min Window Substring, Max Sum K |
| Binary Search | Sorted data, or “find minimum X such that…” | Rotated Array, Koko Bananas, Median of Two Arrays |
| Stack | Next greater/smaller, matching, undo | Daily Temperatures, Valid Parentheses, Largest Rectangle |
| Linked List | Pointer manipulation, cycles, merge | Reverse, Cycle Detection, LRU Cache, Merge K Sorted |
| Trees | Hierarchy, recursion, level-order | Max Depth, Validate BST, LCA, Serialize/Deserialize |
| Graphs (BFS/DFS) | Shortest path, connectivity, islands | Number of Islands, Word Ladder, Course Schedule |
| Dynamic Programming | Overlapping subproblems, count ways / min cost | Coin Change, LIS, Edit Distance, Knapsack |
| Greedy | Locally optimal → globally optimal | Merge Intervals, Jump Game, Activity Selection |
| Backtracking | All combinations/permutations, constraint satisfaction | Subsets, Permutations, N-Queens, Word Search |
| Heap | Top K, merge K sorted, running median | Kth Largest, Find Median, Task Scheduler |
| Union-Find | Connected components, merge groups | Components Count, Accounts Merge, Redundant Connection |
| Trie | Prefix search, autocomplete, word dictionaries | Implement Trie, Word Search II, Autocomplete |
| Topological Sort | Dependencies, ordering, cycle detection | Course Schedule, Alien Dictionary, Build Order |
📖 Deep dive on each pattern with code templates → DSA Fundamentals
✅ Problems with Full Solutions
Each solution includes: approach explanation, walkthrough, complexity analysis, and Java / Python / C++ tabbed code.
| # | Problem | Pattern | Difficulty | Companies |
|---|---|---|---|---|
| 1 | Two Sum II (Sorted Array) | Two Pointers | Easy | Amazon, Google, Microsoft |
| 2 | Longest Substring Without Repeating | Sliding Window | Medium | Amazon, Google, Meta, Bloomberg |
| 3 | Coin Change | Dynamic Programming | Medium | Amazon, Google, Meta, Goldman |
| 4 | Merge Intervals | Greedy / Intervals | Medium | Amazon, Google, Meta, Microsoft |
More solutions added weekly. Drop a request in the comments below 👇
📊 How to Practice Effectively
- Pattern-first, not problem-first. Learn the pattern → solve 3-5 problems → move to the next.
- Time yourself. 25 min per problem. Stuck at 15 min → read the approach (not code), retry.
- Explain out loud. If you can’t explain it in English, you’ll freeze in the interview.
- Spaced repetition. Solve → wait 3 days → re-solve without looking.
- Track progress. Use the checkboxes on each cheatsheet page to track what you’ve done.
Target: 100-150 problems across all patterns, 3 per day, 6-8 weeks.
🔗 Quick Links
| Resource | What it is |
|---|---|
| DSA Fundamentals | 12 patterns explained with multi-language code templates |
| Quick-Fire 50 | The one-page bookmark for last-minute prep |
| The 75 | The interview sprint — 4-5 weeks to cover everything |
| The 150 | Deep coverage — 6-8 weeks, leaves no gaps |
Happy prepping. Drop a comment below if you want a specific problem solved 👇
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