5 Days.
75 Problems.
1 Offer.
Structured day-by-day roadmap from arrays to system design. Every NeetCode 75 problem with brute-force → optimal solution. System design with ratios, trade-offs, and bottlenecks.
Master the HashMap pattern — it solves 40% of all array problems.
Binary search is a mindset — use it whenever you see 'sorted' or 'minimum/maximum k'.
Trees are the most common SDE 2 topic. Know recursive DFS cold.
DP = recursion + memoization. Draw the recurrence tree first.
System design wins SDE 2. Spend 5h on this day. Think in trade-offs.
Fundamentals & Numbers
Latency, CAP, availability, ratios, estimation
URL Shortener
Base62, hashing, caching, redirection at scale
Twitter / News Feed
Fan-out, celebrity problem, feed ranking
Rate Limiter
Token bucket, sliding window, Redis atomicity
Distributed Cache
Redis vs Memcached, eviction, consistency
Notification System
Multi-channel, dedup, retry, priority queues
| Problem Trigger | Pattern to Use | Complexity |
|---|---|---|
| Pair/triplet summing to X | Two Pointers or HashMap | O(n) |
| Longest/shortest subarray with constraint | Sliding Window | O(n) |
| Sorted array, find element | Binary Search | O(log n) |
| Tree path / depth | DFS (recursion) | O(n) |
| Shortest path (unweighted) | BFS (queue) | O(V+E) |
| Shortest path (weighted) | Dijkstra (min-heap) | O(E log V) |
| Detect cycle in graph | DFS with states / Union-Find | O(V+E) |
| Order with dependencies | Topological Sort | O(V+E) |
| Min/max over subproblems | Dynamic Programming | O(n²)–O(n·m) |
| K largest/smallest | Min-Heap of size K | O(n log k) |
| Overlapping intervals | Sort by start + stack/heap | O(n log n) |
| Palindrome / match | Expand from center / Two Pointers | O(n) |