LeetCode in Kotlin
507. Perfect Number
Easy
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
Solution
class Solution {
fun checkPerfectNumber(num: Int): Boolean {
var s = 1
for (sq in Math.sqrt(num.toDouble()).toInt() downTo 2) {
if (num % sq == 0) {
s += sq + num / sq
}
}
return num != 1 && s == num
}
}