507. Perfect Number

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 = 6
Output: true

Example 3:

Input: num = 496
Output: true

Example 4:

Input: num = 8128
Output: true

Example 5:

Input: num = 2
Output: false

 

Constraints:

  • 1 <= num <= 108

Rust Solution

struct Solution;

impl Solution {
    fn check_perfect_number(num: i32) -> bool {
        if num == 1 {
            return false;
        }
        let mut i = 2;
        let mut sum = 1;
        while i * i <= num {
            if num % i == 0 {
                sum += i;
                sum += num / i;
            }
            i += 1;
        }
        sum == num
    }
}

#[test]
fn test() {
    assert_eq!(Solution::check_perfect_number(28), true);
}

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