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