TL;DR (Frontend Version)

• Most frontend DSA = arrays + strings + hashing
• Kill nested loops with:
  • HashMap
  • Two Pointers
  • Sliding Window
• If sorted → think two pointers
• If “longest/shortest subarray/substring” → sliding window
• If “seen before?” → hash set/map

1️⃣ Core Patterns You Actually Need

🟢 1. Hashing (MOST IMPORTANT)

Frontend interviews LOVE this.

Use when:

• Need O(1) lookup
• Counting frequency
• Detect duplicates
• Complements (Two Sum)

Common cues:

• “seen before”
• “first unique”
• “frequency”
• “anagram”