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;
}
}
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Original author: Jake Tao Source: 「507. Perfect Number」
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