Container With Most Water, 3Sum Closest & Squares Array - Two Pointer Pro | DSA Day 16 Java

Day 16 of Complete DSA Series in Java | Two Pointer Technique Mastery - 3 Must-Know FAANG Problems

In this lecture, I solve 3 advanced two pointer problems that are absolute favorites in technical interviews! These problems test your optimization skills and are frequently asked at Google, Amazon, Facebook, and other top tech companies.

Problems Covered:
1️⃣ Container With Most Water - https://leetcode.com/problems/container-with-most-water/
Companies: Google, Facebook, Amazon, Adobe
2️⃣ 3Sum Closest - https://leetcode.com/problems/3sum-closest/description/
Companies: Adobe, Amazon, Apple, Bloomberg, Facebook, Goldman Sachs, Google, Microsoft, Uber
3️⃣ Squares of a Sorted Array - https://leetcode.com/problems/squares-of-a-sorted-array/description/

Companies: Adobe, Amazon, Apple, Bloomberg, eBay, Facebook, Google, Microsoft, Oracle, PayPal
Timestamps:
00:00 - Introduction & Two Pointer Recap
03:15 - Container With Most Water - Problem Visualization
15:30 - 3Sum Closest - Problem Understanding
23:30 - Squares of Sorted Array - The Twist

What You'll Learn:
✅ Greedy algorithm with two pointer technique
✅ Area Maximization using pointer movement logic
✅ Three pointer technique for triplet problems
✅ Sorting + two pointer combination strategy
✅ Tracking closest sum/difference efficiently
✅ Handling negative numbers in sorted arrays
✅ Building result arrays using two pointers
✅ Why moving the smaller value works (mathematical proof)
✅ Optimizing from O(n²) to O(n) solutions
✅ When to move left vs right pointer

Why These Problems Matter:
🎯 Container With Most Water - Classic greedy + two pointer problem, tests optimization intuition
🎯 3Sum Closest - Extends 3Sum pattern, critical for understanding triplet problems
🎯 Squares Array - Perfect example of two pointer on arrays with negative numbers
🎯 These patterns appear in 40+ similar interview problems
🎯 Master the decision-making: which pointer to move?
🎯 All are medium-level problems asked in 80% of FAANG interviews

Complexity Analysis:
Container With Most Water: O(n) time, O(1) space
3Sum Closest: O(n²) time, O(log n) space (sorting)
Squares of Sorted Array: O(n) time, O(n) space

Key Patterns Mastered:
🔥 Greedy Two Pointer - Move pointer that limits the result
🔥 Three Pointer Technique - Fixed + two moving pointers
🔥 Bidirectional Merging - Build result from both ends
🔥 Sorted Array Optimization - Leverage sorted property

Perfect for:
Advanced DSA learners mastering two pointer
Students preparing for medium-hard interview questions
Engineers targeting senior roles at FAANG/MAANG
Anyone wanting to master greedy algorithms
College students in final placement rounds
Developers learning optimization techniques
Problem Difficulty Progression: Container With Most Water: Medium ⭐⭐⭐ 3Sum Closest: Medium ⭐⭐⭐⭐ Squares of Sorted Array: Easy ⭐⭐

Resources:
GitHub Code: https://github.com/PrepInstaPrime/DSA-series-NextGen/tree/main/day16
Playlist Link: https://www.youtube.com/playlist?list=PLiwJ_dZwC5aJeFvMXrERkhre0VkNqohZR

About Me: I'm Gaurav Pandey, and I'm here to help you master Data Structures and Algorithms in Java. This is part of our comprehensive DSA series on Next Gen Skills where we tackle increasingly challenging problems with proven patterns.

LinkedIn for personal doubts: https://www.linkedin.com/in/gaurav-pandey-00b75126a/?originalSubdomain=in

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Previous Video: https://www.youtube.com/watch?v=iUB8gLPaUa4

Complete Playlist: https://www.youtube.com/playlist?list=PLiwJ_dZwC5aJeFvMXrERkhre0VkNqohZR

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