Perfect Number
一个数是Perfect number就是他的factor的和等于这个数. 那么先求factor, 然后求和就可以了.
class Solution {
public boolean checkPerfectNumber(int num) {
if(num <= 0)
return false;
int sum = 0;
for(int i = 1; i <= Math.sqrt(num); i++) {
if(num % i == 0) { // if it is a factor
sum += i;
if (i * i != num) { // adding num / i
sum += num / i;
}
}
}
System.out.println(sum);
return sum - num == num;
}
}