Most coding interview questions don’t test how many problems you’ve memorized. They test whether you recognize the pattern hiding in plain sight. Once that clicks, interviews stop feeling like chaos and start feeling… familiar. Here are the most common DSA patterns every interview-ready developer should have on speed dial: 1. Hashing (HashMap / HashSet) When things get hard… throw a HashMap at it.Use it for: - Fast lookups - Counting frequencies - Tracking visited elements - Turning O(n²) pain into O(n) peace 2. Two Pointers Two indices, one elegant solution. Perfect for: - Sorted arrays - Pair problems - Reversals and partitions 3. Sliding Window For anything involving subarrays or substrings Best when: - You need max/min/length - The window grows and shrinks intelligently 4. Binary Search Not just for “find X in sorted array”. Use it when: - The answer space is sorted - You’re minimizing or maximizing something - You hear the words “minimum possible” or “maximum feasible” 5. Stack When order matters and you need to go back. Think: - Valid parentheses - Next greater/smaller element - Undo operations 6. BFS / DFSF or trees, graphs, and grids. Choose: - BFS for shortest paths - DFS for depth, paths, and exploration The real unlock? 👉 Interview questions repeat. Patterns repeat harder. Once you train your brain to spot patterns first,coding becomes execution, not panic. Practice problems, yes. But master the patterns: that’s how you walk into interviews calm, clear, and dangerous (in a good way).