### 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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