Problem
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)
Solution
class Solution {
public boolean checkPerfectNumber(int num) {
if (num == 1) return false;
int sum = 1;
for (int i = 2; i <= Math.sqrt(num); i++) {
int remainder = num % i;
if (remainder == 0) {
sum += i + num/i;
}
}
System.out.println(sum);
return sum == num;
}
}
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