LeetCode 633. Sum of Square Numbers

Description

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

Analysis

这道题不需要很复杂的数论知识，纯暴力也可以过，但两层循环遍历可能的数字会TLE，要利用

a

,

b

两数之间的关系，一层循环即可，直接利用sqrt()函数和强制类型转换即可AC。

Code

class Solution {
public:
bool judgeSquareSum(int c) {
for (long a = 0; a * a <= c; a++){
double b = sqrt(c - a * a);
if ((int)b == b)
return true;
}
return false;
}
};

Appendix

Link: https://leetcode.com/problems/sum-of-square-numbers/

Run Time: 13ms