LeetCode #3719 Explained | Longest Balanced Subarray I | Prefix Sum + HashMap

LeetCode #3719 Explained | Longest Balanced Subarray I | Prefix Sum + HashMap

In this video, we solve LeetCode Problem #3719 – Longest Balanced Subarray I, an important array and prefix sum problem frequently asked in coding interviews.

The goal is to find the length of the longest balanced subarray, where the count of distinct even numbers equals the count of distinct odd numbers.

The solution is explained step by step using an efficient Prefix Sum + HashMap approach, making it easy to understand and implement.

Problem Overview

You are given an integer array

A subarray is called balanced if:

Number of distinct even elements = number of distinct odd elements

Return the maximum length of such a subarray

Approach Explained

Convert the problem into a prefix difference problem

Track the balance between even and odd elements

Use a HashMap to store first occurrences

Update the maximum length whenever the balance repeats

This approach runs efficiently in O(n) time.

What You Will Learn

How to identify balanced subarrays

Applying prefix sum techniques

Using HashMap for optimized lookup

Writing interview-ready array solutions

Time and space complexity analysis

📄 PDF Notes & 💻 Code Resources

Access PDF notes and full code explanations here:
👉 https://github-website-ochre.vercel.app/

💻 DSA & LeetCode Playlist

Complete DSA playlist with explanations and animations:
👉 https://github.com/sannikumar85/DSA_Playlist_by_Animation

👨‍💻 Connect With Me

LinkedIn Profile:
👉 https://www.linkedin.com/in/sanni-kumar-gupta-10792b290/

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