367.Valid-Perfect-Square.cpp

class Solution {
public:
    bool isPerfectSquare(int num) {
        if (num == 1) return true;
        long long l = 1, r = num / 2;
        
        while(l <= r) {
            long long mid = (l + r) / 2;
            long long square = mid * mid;
            
            if (square == num) return true;
            else if (square < num) l = mid + 1;
            else r = mid - 1;
        }
        
        return false;
    }
};