Leetcode633.Sum of Square Numbers平方数之和

给定一个非负整数 c ，你要判断是否存在两个整数 a 和 b，使得 a2 + b2 = c。

示例1:

输入: 5 输出: True 解释: 1 * 1 + 2 * 2 = 5

示例2:

输入: 3 输出: False

方法一：
class Solution {
public:
    bool judgeSquareSum(int c) {
        for(int i = sqrt(c); i >= 0; i--)
        {
            int j = sqrt(c - i * i);
            if(i * i + j * j == c)
                return true;
        }
        return false;
    }
};
方法二：
class Solution {
public:
    bool judgeSquareSum(int c) {
        int low = 0;
        int high = sqrt(c);
        while(low <= high)
        {
            int mid = low * low + high * high;
            if(mid == c)
                return true;
            else if(mid > c)
            {
                high--;
            }
            else
            {
                low++;
            }
        }
        return false;
    }
};