difference of 2 arrays

[cmb3587]

I have two arrays and I'm trying to create a 3rd array that is the difference between the two arrays

Ex:

arrayA: 3 5 8 9
arrayB: 3 4 6 9

difference of A-B: 5 8

however, my code is just returning me an array of 0's

im trying to use my search method (which has been tested and works) to take a number from the first array and search it in the other array. If it is not found the search method returns a 0 and the number from the first array is then stored into the 3rd array.

here is the portion of my code, I'm not sure what is wrong.

//Cory Boughton
 
import java.util.*;
 
public class Sets {
 
    public static Scanner kbd = new Scanner (System.in);
 
    public static final int MAXSIZE = 20;
 
    public static void main(String[] args) {
 
        int[]setA = new int[MAXSIZE];
        int[]setB = new int[MAXSIZE];
        int[]intersect = new int [MAXSIZE];
        int[]difference = new int [MAXSIZE];
        int sizeA, sizeB, interSize, diffSize;
 
        System.out.print("How many numbers will be in the 1st set: ");
        sizeA = kbd.nextInt();
        while (sizeA > MAXSIZE){
            System.out.print("Error: Set size is too large. Re-enter set size: ");
            sizeA = kbd.nextInt();
        }
        System.out.println("Enter list of integers for 1st set: ");
        getData(setA, sizeA);
 
        System.out.print("How many numbers will be in the 2nd set: ");
        sizeB = kbd.nextInt();
        while (sizeB > MAXSIZE){
            System.out.print("Error: Set size is too large. Re-enter set size: ");
            sizeB = kbd.nextInt();
        }
        System.out.println("Enter list of integers for 2nd set: ");
        getData(setB, sizeB);
 
        interSize = intersection(setA, sizeA, setB, sizeB, intersect);
        System.out.print("The intersection of the two sets is: ");
        for (int x = 0; x < interSize; x++){
            System.out.print(intersect[x] + " ");
        }
 
        diffSize = difference(setA, sizeA, setB, sizeB, intersect);
        System.out.print("\n\nThe difference of A-B is: ");
        for (int x = 0; x < diffSize; x++){
            System.out.print(difference[x] + " ");
        }
    }
 
    public static void getData(int[]set, int size){
 
        for(int x = 0; x < size; x++){
            int num = kbd.nextInt();
            int count = search(set, size, num);
            if (count == 0)
                set[x] = num;
            else 
                x--;
        }
    }
 
    public static int search(int[]set, int size, int num){
 
        int count = 0;
 
        for (int x = 0; x < size; x++){
            if (num == set[x])
                count++;
        }
        return count;
    }
public static int difference(int[]setA, int sizeA, int[]setB, int sizeB, int[]resultSet){
 
        int y = 0;
        for (int x = 0; x < sizeA; x++){
            int num = setA[x];
            int found = search(setB, sizeB, num);
            if (found == 0){
                resultSet[y] = num;
                y++;
            }
        }
        return y;
    }
}
 

[dmjpro]

@cmb3587
On the basis of which logic you are saying the difference ?

[JosAH]

@dmjpro
From ordinary set theory: A-B are all elements in A that are not in B.

kind regards,

Jos

[r035198x]

Why not have a look at the ArrayList class and see what magic you can conjure up with it?

[dmjpro]

See you better to use Collection instead of Array.
If you use Collection then you will find better APIs to do your work easily.

List set_a;
List set_b;
List set_c;
 
for(int i=0;i<set_a.size();i++){
 if(set_b.indexOf(set_a.get(i))!=-1) set_c.add(set_a.get(i));
}
 

[r035198x]

@dmjpro, if you keep looking at the API you will find cleaner and even easier ways of doing it.

[dmjpro]

@r035198x
Sorry i couldn't find it any? ;)

[r035198x]

For starters you could have used the contains method.

For blatant cheaters you could look at retainAll combined with removeAll.

[dmjpro]

Ahh! actually "retainAll" method stroke my brain.
Anyway what i could figure out ...

List set_a;
List set_b;
 
List temp_set = set_a.clone();
temp_set.retainAll(set_b); //it finds out the common elements between two sets.
set_a.removeAll(temp_set); //now the final desired set is ready
 

That's what you said.
When do you make method call then i think lots of headache is up to RunTime System. What you think which one would be the better solution?

[JosAH]

@r035198x
I don't understand the 'blatant cheaters' part ...

kind regards,

Jos ;-)