CODEWITHSUNDEEP
javaarrays
a24
a24

Reputation: 7

How to compare each integer in 2 arrays

This is my assignment:

Assume U = {1 , . . . ,10 }. Write a Java program which lets you enter a pair of sets A & B from the keyboard, then computes and prints their union and intersection. Remember that the sets of A and B must be a subset of the U(universe) set.

Right now my main concern is how to compare each index from the two arrays I have. If the indexes match, then I need it to be true, otherwise if they don't match, I need it to be false. I just don't know how to compare the two so if someone could give me some guidance, that'd be great. (I realize I don't have anywhere in my code comparing the two, I just am unsure of where to begin with it).

Here's my code:

import java.util.*;
public class sets {
    public static void main (String[] args) {
    Scanner console = new Scanner(System.in);

      //Declare the variables
      int [] universe = new int[10];

      //Ask the user for the numbers in set A
      System.out.print("How many numbers do you want in the first set? ");
      int num1 = console.nextInt();
      int [] A = new int [num1];
      int i = 0;
      while (i < num1) {
         System.out.print("Please enter an integer 1-10: ");
         int numA = console.nextInt();
         A[i++] = numA;
      }

      //Ask the user for the numbers in set B  
      System.out.print("How many numbers do you want in the second set? ");
      int num2 = console.nextInt();
      int [] B = new int [num2];
      int j = 0;
      while (j < num2) {
         System.out.print("Please enter an integer 1-10: ");
         int numB = console.nextInt();
         B[j++] = numB;
      }


      System.out.println(Arrays.toString(A));
      System.out.println(Arrays.toString(B));
   }
}

Upvotes: 0

Views: 101

Answers (2)

njzk2
njzk2

Reputation: 39386

Disclaimer: As this is apparently a homework, I will not post any code per se.

The first thing you need to do is define the 3 notions you use in this exercise:

  • A set is a group of elements such as each element is present only once
  • An intersection is a set of element present in group A or in group B
  • An union is a set of element present both in group A and in group B

Then you need to define what basic functions you will need.

  • tell if an element E is present in a set A.
  • add an element to a set.

Now, looking at what you have so far, the issue is that you are creating 2 groups A and B that are not sets. There is nothing preventing to have a group like so [1, 1, 1]

Therefore, you first work should be to make sure each group remains a set, by checking the content of the set before adding a value. That uses the first function defined earlier.

Once A and B are both sets, you need to find an algorithm for each of the functions that are asked of you.

The union algorithm is quite simple:

  • Loop on the elements of each of the groups that you want to add to the union, if the element is not in the set already, add it.

The intersection is not very much complicated:

  • Loop on the elements of each of the groups that you want to add to the union, if the element is not in the set already, and is present in all the groups that you are intersecting, add it.

All this should fit in around 20 lines, 30 tops.

Upvotes: 0

peter.petrov
peter.petrov

Reputation: 39437

Declare two methods

private static int[] union(int[] s1, int[] s2)

and

private static int[] intersection(int[] s1, int[] s2)

See if you can generate their return values
from the int[] values (i.e. the sets) passed in.

Alternatively, you can avoid all the trouble, and just use
HashSet<Integer> instead of int[] for representing your
sets. But I guess you want to do everything yourself which is
better (as this is just an exercise).

Upvotes: 1

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