Valid Perfect Square

Given a positive integer num, write a function which returns True if num is a perfect square else False.

Note: Do not use any built-in library function such as sqrt.

Example 1:

Input: 16
Returns: True
Example 2:

Input: 14
Returns: False

方法：二分法，注意精度

class Solution {
private:
    bool binarySort(int num){
        int left = 0, right = num/2;
        bool isHas = false;
        while(left<=right){
            long middle = left + (right - left) /2;
            if(middle*middle==num){
                isHas = true;
                break;
            }
            else if (middle * middle >num)
                right = middle - 1;
            else
                left = middle + 1;
        }
        return isHas;
    }

public:
    bool isPerfectSquare(int num) {
        return num==1?true:binarySort(num);
    }
};