LeetCode 633. Sum of Square Numbers

633. Sum of Square Numbers

Descripiton

Given a non-negative integer c, your task is to decide whether there’re two integers a and b such that a2 + b2 = c.

Example 1:

Input: 5
Output: True
Explanation: 1 * 1 + 2 * 2 = 5

Example 2:

Input: 3
Output: False

Solution

题意即判断一个数能够由两个数的平方和表示。

我们可以枚举a、b，a从0开始，b从c的开方开始，并根据大小调节a、b的遍历规则。代码如下：

bool judgeSquareSum(int c) {
int a = 0,b = floor(sqrt(c));
while (a <= b) {
int t = a * a + b * b;
if (t == c)
return true;
else if (t > c)
b--;
else
a++;
}
return false;
}