1.题目
Given a non-negative integer c, your task is to decide whether there’re two integers a and b such that a2 + b2 = c.
给一个数字C,判断C是否能由两个数的平方组成
Example 1:
Input: 5
Output: True
Explanation: 1 * 1 + 2 * 2 = 5
Example 2:
Input: 3
Output: False
2.分析
要找出是否存在a2 + b2 = c. 先限定a,b的范围。 0<=a,b<=sqrt(c)
然后从两端向中间逼近。
3.代码
class Solution {
public:
bool judgeSquareSum(int c) {
int left = 0, right = sqrt(c);
while (left <= right) {
int result = left*left + right*right;
if (result == c)
return true;
else if (result < c)
++left;
else
--right;
}
return false;
}
};