[leetcode]633. Sum of Square Numbers平方数之和

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

 

题意：

给定非负整数c，问是否存在整数a、b，使得 a² + b² = c

 

code

class Solution {
     public boolean judgeSquareSum(int c) {
        if (c < 0) {
            return false;
        }
        int left = 0, right = (int)Math.sqrt(c);
        while (left <= right) {
            int cur = left * left + right * right;
            if (cur < c) {
                left++;
            } else if (cur > c) {
                right--;
            } else {
                return true;
            }
        }
        return false;
    }
}