Interview Question Series | Season 3 | Episode 17

In this video, we break down LeetCode Problem 367 – Valid Perfect Square using C++.

This problem is frequently asked in interviews at companies like Microsoft, Meta, Amazon, and Google — it tests your ability to efficiently determine if a number is a perfect square without using any built-in square root functions.

You’ll learn how to check if a positive integer num can be expressed as the square of another integer, using a binary search approach that avoids brute force multiplication.

We’ll walk step by step through the logic, showing how to:

* Use binary search to find the integer whose square might equal num
* Compare the mid-value squared with num to decide which half of the search space to explore
* Handle large numbers safely without integer overflow
* Return true if a perfect square exists, or false otherwise

By the end, you’ll understand how to:

* Implement an O(log n) time and O(1) space solution — optimal even for the largest allowed input of 2³¹ - 1
* Avoid using sqrt or other built-in functions while keeping your code clean and efficient
* Solve this classic “check perfect square” problem in interviews confidently

This method is a must-know technique for any coding interview, showing mastery of binary search for numeric problems.

Видео Interview Question Series | Season 3 | Episode 17 канала Fuzetek