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)
class Solution { public boolean checkPerfectNumber(int num) { if(num == 1) return false; int sum = 0; for(int i=2; i<=Math.sqrt(num);i++){ if(num%i == 0){ sum += i; if(num/i != i) sum += num/i; } } return sum+1 == num; } } This siteOriginal articleAll follow "Attribution-NonCommercial-ShareAlike 4.0 License (CC BY-NC-SA 4.0)Please retain the following annotations when sharing or adapting:
Original author:Jake Tao,source:"507. Perfect Number"
