Amazon Practice 2

amazon2.java

// IMPORT LIBRARY PACKAGES NEEDED BY YOUR PROGRAM
// SOME CLASSES WITHIN A PACKAGE MAY BE RESTRICTED
// DEFINE ANY CLASS AND METHOD NEEDED
// CLASS BEGINS, THIS CLASS IS REQUIRED
import java.util.*;
class GCD
{
    // METHOD SIGNATURE BEGINS, THIS METHOD IS REQUIRED
    public int generalizedGCD(int num, int[] arr)
    {
        if(arr.length==0) return 0;
        List<Integer> commonDivisors = primeDivisors(arr[0]);
        for(int i=1; i<arr.length; i++){
            commonDivisors.retainAll(primeDivisors(arr[i]));
        }
        
        int result = 1;
        for(int j=0; j<commonDivisors.size(); j++){
            result *= commonDivisors.get(j);
        }
        return result;
    }
    
    public List<Integer> primeDivisors(int num){
        List<Integer> divisors = new ArrayList<Integer>();
        divisors.add(1);
        if(num%2 == 0) divisors.add(2);
        for(int i=3; i<Math.sqrt(num); i+=2){
            if(num%i == 0) divisors.add(i);
        }
        return divisors;
    }
    
    public int smallestPrimeDivisor(int num){
        if(num%2 == 0) return 2;
        for (int i=3;i<Math.sqrt(num);i+=2)
        {
            if (num%i==0) return(i);
        }  
        return(num);
    }
    // METHOD SIGNATURE ENDS
}