Valid Perfect Square

Given a positive integer num, write a function which 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
Returns: True

Example 2:

Input: 14
Returns: False

Credits:
Special thanks to @elmirap for adding this problem and creating all test cases.

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public class Solution {
    public boolean isPerfectSquare(int num) {
        long start = 0;
        long end = num/2;
        if(num==1)return true;
        while(start<=end)
        {
            long mid = (long)start + (end-start)/2;
            long val = (long)mid * mid;
            if(val==num) return true;
            else if(val<num)
            {
                start = mid+1;
            }
            else
            {
                end = mid-1;
            }
        }
        
        return false;
    }
}