c++二分法求一个数的完全平方数

java版：
class Solution {
    private int low=0;
    private int high=0;
    public boolean isPerfectSquare(int num) {
        if(num==1)return true;
        low=0;
        high=num>>1;
        while(low<=high)
        {
            long mid = (low+high)>>1;
            long res=mid*mid;
            if(res>num)high=(int) (mid-1);
            else if(res<num)low=(int)(mid+1);
            else if(res==num)return true;          
        }
        return false;
    }
}

/***
 * 问题：有效的完全平方数
 * 原理：一个数为完全平方数则必是某个数的平方
 * 并且这个数要小于等于它的一半，如4为2的平方
*/
class Solution {
private:
    int low=0;
    int high=0;
public:
    bool isPerfectSquare(int num) {
        low=0;
        high=num>>1;
        while(low<=high)
        {
            int mid=(low+high)>>1;
            int res=mid*mid;
            if(num>res)low=mid+1;
            else if(num<res)high=mid-1;
            else if(num==res) {
               return true;
            }
        }
        return false;
    }
};