🎯 Two-Pointer Technique: Essential Pattern for Frontend Interviews
Category: dsa
Difficulty: hard
Interview Importance: 🔴 Critical — This technique appears in 40% of frontend coding interviews for array/string manipulation problems. Understanding this pattern is essential for solving problems efficiently without nested loops. 1️⃣ What is the Two-Pointer Technique? The Two-Pointer Technique is an algorithmic pattern that uses two pointers (indices) to traverse a data structure, typically an array or string. Instead of using nested loops (O(n²)), we use two pointers moving intelligently through the data to achieve O(n) time complexity. Visual Representation: [code example] Real-World Analogy: Think of it like two people searching through a bookshelf from opposite ends to find a matching pair of books. Instead of one person checking every combination (which would take forever), both people work simultaneously, making the search much faster. 2️⃣ Why Use the Two-Pointer Technique? Without Two-Pointer Benefit O(n²) nested loops 100x faster for 1000 items Remove duplicates O(n) in-place O(n) extra space 50% memory saved Palindrome check O(n) convergence O(n*m) brute force Linear scaling | Performance Benefits: Reduces time complexity from O(n²) to O(n) in most cases Often achieves O(1) space complexity (in-place operations) Perfect for frontend scenarios: filtering lists, validating inputs, processing user data 3️⃣ How It Works — Basic Implementation Pattern 1: Opposite Direction (Converging Pointers)...