Solution.java

class MyCalculator implements AdvancedArithmetic {
 // Time Complexity: O(n^(1/2))
 // Space Complexity: O(1)
 public int divisor_sum(int n) {
 int sum = 0;
 int sqrt = (int) Math.sqrt(n);
 for (int i = 1; i <= sqrt; i++) {
 if (n % i == 0) { // if "i" is a divisor
 sum += i + n/i; // add both divisors
 }
 }
 /* If sqrt is a divisor, we should only count it once */
 if (sqrt * sqrt == n) {
 sum -= sqrt;
 }
 return sum;
 }
}