Perfect Number
We define the Perfect Number is a positive integer that is equal to the sum of all its positive divisors except itself.
Now, given an integer n, write a function that returns true when it is a perfect number and false when it is not.
Example:
Input: 28 Output: True Explanation: 28 = 1 + 2 + 4 + 7 + 14
Note: The input number n will not exceed 100,000,000. (1e8)
1 public class Solution { 2 public boolean checkPerfectNumber(int num) { 3 if (num <= 1) return false; 4 5 int sum = 1; 6 for (int i = 2; i <= Math.sqrt(num); i++) { 7 if (num % i == 0) 8 sum += i + num / i; 9 } 10 return sum == num; 11 } 12 }