LeetCode "Valid Perfect Square"

Typical binary search.. but take care of data overflow if you are using C++

class Solution {
public:
    bool isPerfectSquare(int num) {
        if(num < ) return false;
        if(num < ) return true;

        long long i = , j = num - ;
        while(i <= j)
        {
            long long mid = (i + j) / ;
            long long r = mid * mid;

            if(r == num) return true;
            if(r < num) i = mid + ;
            else j = mid - ;
        }
        return false;
    }
};