// @Title: 有效的完全平方数 (Valid Perfect Square)
// @Author: qisiii
// @Date: 2024-09-06 17:21:32
// @Runtime: 0 ms
// @Memory: 39.5 MB
// @comment: 
// @flag: 
class Solution {
    public boolean isPerfectSquare(int num) {
        int left=1,right=num;
        while(left<=right){
            int mid=left+(right-left)/2;
            long sum=(long)mid*mid;
            if(sum==num){
                return true;
            }else if(sum>num){
                right=mid-1;
            }else{
                left=mid+1;
            }
        }
        return false;
    }
}