Write a static method named mergeSortedLists that takes two ArrayLists of Intege

Question

Write a static method named mergeSortedLists that takes two ArrayLists of Integers that are in increasing order and returns a new ArrayList of Integers that contains the elements of the original lists "merged" together in increasing order. For example, if the first list contains the elements [1, 4, 4, 7, 22] and the second list is [3, 3, 5, 5, 21, 25, 30] then the new list should be [1, 3, 3, 4, 4, 5, 5, 7, 21, 22, 25, 30]. Again, if one list is longer than the other append the remaining elements to theend of the new list.

Explanation / Answer

I have written the program in Java using ArrayList. Below is the program

import java.util.ArrayList;
import java.util.Arrays;

public class mergeTest {
  
   public static ArrayList<Integer> mergeSortedLists(ArrayList<Integer> list1, ArrayList<Integer> list2)
   {

   ArrayList<Integer> output = new ArrayList<Integer>();
   int i = 0, j = 0, k = 0;
   // this loop will compare the 2 elements of different lists, and copy the smaller into output
   while (i < list1.size() && j < list2.size())
   {
   if (list1.get(i) < list2.get(j))
   {
       output.add(list1.get(i));
   i++;
   }
   else
   {
       output.add(list2.get(j));
   j++;
   }
   k++;
   }
   // the below 2 loops copy the entire list into output once the list exhausted
   while (i < list1.size())
   {
       output.add(list1.get(i));
   i++;
   k++;
   }

   while (j < list2.size())
   {
       output.add(list2.get(j));
   j++;
   k++;
   }

   return output;
   }
  
   public static void main(String[] args) {

      
       ArrayList<Integer> list1 = new ArrayList<Integer>(Arrays.asList(1, 4, 4, 7, 22));
       ArrayList<Integer> list2 = new ArrayList<Integer>(Arrays.asList(3, 3, 5, 5, 21, 25, 30));
      
       System.out.println(" list 1 input ");
       for(int item : list1)
       {
           System.out.println(item);
       }
      
       System.out.println(" list 2 input ");
       for(int item : list2)
       {
           System.out.println(item);
       }
      
       ArrayList<Integer> sortedList = mergeSortedLists(list1,list2);
      
       System.out.println("");
       System.out.println("merged list after sorting");
      
               for(int item : sortedList)
       {
           System.out.println(item);
       }
   }

}

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