A perfect number is a positive integer that is equal to the sum of its positive divisors, excluding the number itself. A divisor of an integer x is an integer that can divide x evenly.
Given an integer n, return true if n is a perfect number, otherwise return false.
Example 1:
Input: num = 28 Output: true Explanation: 28 = 1 + 2 + 4 + 7 + 14 1, 2, 4, 7, and 14 are all divisors of 28.
Example 2:
Input: num = 7 Output: false
Constraints:
1 <= num <= 108
Companies:
Adobe
Related Topics:
Math
Similar Questions:
// OJ: https://leetcode.com/problems/perfect-number/
// Author: github.com/lzl124631x
// Time: O(sqrt(N))
// Space: O(1)
class Solution {
public:
bool checkPerfectNumber(int n) {
if (n == 1) return false;
int sum = 0;
for (int i = 1; i * i <= n; ++i) {
if (n % i) continue;
sum += i;
if (i != 1 && n / i != i) sum += n / i;
if (sum > n) return false;
}
return sum == n;
}
};