Question

Using Java programming,

1. The Set interface in the API has the methods addAll(Collection<? extends E> c) and retainAll(Collections<? > c), which acts like union and intersection respectively. However, these modify the set it is called on. This means after set1.addAll(set2) or set1.retainsAll(set2) is executed, set1 will be the union or intersection of the two sets, respectively.
   
2. Choose ONE of the implementations below
   1. Ordered lists
   2. Binary search trees
   3. Hash tables
      
3. Add a method in that implementation that returns the union of the two sets but does not change either set. This mean your method should find the union and return it. Make sure to test your method for correctness.
   
4. Include a worst case running time of your method.

Answer 1

import java.lang.*;
import java.util.*;

//list class
class name_list{
   //declaring the empty arraylist to add inputs strings
   ArrayList<String> first;
   ArrayList<String> second;
   int n=0,m=0;

   //two parameter constructer
   public name_list(int n,int m){
       this.n=n;
       this.m=m;
       //initiating the two array lists
       first = new ArrayList<String>(n+m);
       second = new ArrayList<String>(m);
   }
   //adding the strings to first arraylist
   public void add_elements_first(String value){
       first.add(value);
   }
   //adding the strings to second arraylist
   public void add_elements_second(String value){
       second.add(value);
   }
   //method to find the union of two arralsit
   public ArrayList<String> union(){
       //initializing the empty arraylist to store the union of wo arrays
       ArrayList<String> temp = new ArrayList<String>(n+m);
       //initalizing the iterator to loop through the arraylist
       Iterator<String> itr1 = first.iterator();
       while(itr1.hasNext()){
           temp.add(itr1.next());
           //adding the elements to arraylist
       }
       Iterator<String> itr2 = second.iterator();
       //finding the union
       while(itr2.hasNext()){
           String var =itr2.next();
           if(!temp.contains(var)){
               temp.add(var);
           }
       }
       // Iterator<String> temp1 = temp.iterator();
       // while(temp1.hasNext()){
       //    System.out.println(temp1.next());
       // }
       return temp;
   }
}

class driverCheck{
   public static void main(String[] args) {
       Scanner scan = new Scanner(System.in);
       System.out.println("Enter the size of first queue");
       int n = scan.nextInt();
       System.out.println("Enter the size of second queue");
       int m = scan.nextInt();
       //creating the class object
       name_list obj = new name_list(n,m);
       //looping to read the arraylist elements to first arraylist
       for (int i=0;i<n ;i++ ) {
           System.out.println("Enter the"+i+" value");
           obj.add_elements_first(scan.next());
       }
       //looping to read the arraylist elements to second arraylist
       for (int i=0;i<m;i++ ) {
           System.out.println("Enter the"+i+" value");
           obj.add_elements_second(scan.next());
       }
       System.out.println("\n");
       System.out.println("union");
       //return array list
       ArrayList<String> chk = obj.union();
       Iterator<String> chkitr = chk.iterator();
       while(chkitr.hasNext()){
           System.out.println(chkitr.next());
       }
   }
}

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