633. Sum of Square Numbers

• Difficulty: Easy

• Topics: Math

• Similar Questions:

  • Valid Perfect Square

Problem:

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

Solutions:

class Solution {
public:
    bool judgeSquareSum(int c) {
        long left = 0;
        long right = sqrt(c) + 1;

        while (left <= right) {
            long sum = left * left + right * right;
            if (sum == c)   return true;
            else if (sum > c) {
                --right;
            } else {
                ++left;
            }
        }

        return false;
    }
};