This will help you solve 90% of all DSA problems in interviews (based on my experience over the last 5+ years)

◄ Array / String Inputs

1. Is the array sorted?
→ Use Binary Search, Two Pointers, or Prefix Sums

2. Optimization problems (Max/Min/Subarray)?
→ Think Sliding Window, Dynamic Programming, or Greedy

3. Looking for duplicates / counts / frequencies?
→ Use HashMap, HashSet, or Counting Array

4. Need substrings or fixed-size subarrays?
→ Apply Sliding Window with Two Pointers

5. Frequent min/max in window?
→ Use Monotonic Queue, Deque, or Heap

6. Generating subsets, permutations, combinations?
→ Use Backtracking

7. Matching / parsing characters?
→ Use Stack, especially for Balanced Parentheses, Infix/Postfix

If you want to solve problems fast and with solid accuracy, you need to think in patterns.

Without patterns, you can solve every problem in an interview that you’ve seen once, but once you see a new problem, you will get stuck.