367. 有效的完全平方数

class Solution {
public:
    bool isPerfectSquare(int num) {
        int left = 0, right = num;
        while(left <= right){
            int mid = left + (right - left) / 2;
            if(pow(mid, 2) == num){
                return true;
            }else if(pow(mid, 2) > num){
                right = mid - 1;
            }else{
                left = mid + 1;
            }
        }
        return false;
    }
};