### Perfect Square - The Coding Shala

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## Check if a given number is perfect square or not

In this post, we will see how to check if a given number is a perfect square or not. Given a positive integer num, write a function that returns True if num is a perfect square else False.

Note: Do not use any built-in library function such as sqrt.

Example 1:

Input: 16

Output: true

Example 2:

Input: 14

Output: false

## Java Program to check a perfect square

Approach:

We can use a binary search to check if the given number is a perfect square or not instead of checking number one by one.

Java Code:

class Solution { public boolean isPerfectSquare(int num) { if(num == 1) return true; int left = 1; int right = num/2; while(left < right){ int mid = left + (right-left)/2; if((long)mid*mid == (long)num) return true; if((long)mid*mid > (long)num) right = mid-1; else left = mid+1; } if((long)right*right == (long)num) return true; return false; } }

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