Скачать или смотреть 💥 LeetCode 18: 4Sum | Advanced Two Pointer Pattern for FAANG Coding Interviews!

💥 LeetCode 18: 4Sum | Advanced Two Pointer Pattern for FAANG Coding Interviews!

In this video, we solve LeetCode 18: 4Sum — a high-value variation of the N-Sum pattern that's commonly asked in FAANG and Tier-1 product-based company interviews.

This problem takes the 3Sum logic one step further, adding another level of iteration, while still maintaining O(n³) efficiency using sorting + two-pointer with careful duplicate handling.

🔍 Problem Summary:
Given an array nums and an integer target, return all unique quadruplets [nums[a], nums[b], nums[c], nums[d]] such that:
a ≠ b ≠ c ≠ d and nums[a] + nums[b] + nums[c] + nums[d] == target.

🎯 What You’ll Learn:

How to extend 3Sum logic to 4Sum

Efficient pruning with sorted input

Duplicate skipping tricks

How to generalize to N-Sum recursively

Handling edge cases for large arrays and overflow

💼 Frequently Asked In:

Google (for N-Sum pattern insight)

Amazon (OA and onsite)

Meta (phone + onsite)

Bloomberg

Qualcomm

📌 Problem Link: https://leetcode.com/problems/4sum/

🎓 Also helps with solving:

LeetCode 1: Two Sum

LeetCode 15: 3Sum

LeetCode 16: 3Sum Closest

LeetCode 454: 4Sum II (hashmap variant)

🧠 Part of: “DSA + Binary Search Playlist for Tech Interviews | Google, Meta, Microsoft Prep”

This is a must-master for advanced DSA prep and interviews involving combination sums.