Formatted question description: https://leetcode.ca/all/633.html

633. Sum of Square Numbers

Level

Easy

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

Solution

Maintain two numbers low and high, which are 0 and the greatest integer less than or equal to the square root of c. While low < high, calculate sum = low * low + high * high. If sum == c, then the two integers are found, so return true. If sum > c, then sum is too large, so decrease high by 1. If sum < c, then sum is too small, so increase low by 1. If the two integers can’t be found, return false.

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

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