Question

Complete the following method in java:

public static List<Integer> runningMedianOfThree(List items)

Create and return a new List<Integer> instance (of any subtype of List of your choice) whose first two elements are the same as that of original items, after which each element equals the median of the three elements in the original list ending in that position. For example, when called with a list that prints out as [5, 2, 9, 1, 7, 4, 6, 3, 8], this method would return an object of type List<Integer> that prints out as [5, 2, 5, 2, 7, 4, 6, 4, 6].

Answer 1

Java Program:

import java.util.*;

class MedianList
{
   //Main method
   public static void main(String args[])
   {
       //Creating original list
       List<Integer> orgLst = new ArrayList<Integer>();
      
       //Adding elements
       orgLst.add(5);
       orgLst.add(2);
       orgLst.add(9);
       orgLst.add(1);
       orgLst.add(7);
       orgLst.add(4);
       orgLst.add(6);
       orgLst.add(3);
       orgLst.add(8);
      
       System.out.print("\nOriginal List: ");
          
       //ITerating and printing elements
       for(Integer a:orgLst)
       {
           System.out.print(a + " ");
       }
      
       //Calling function
       List<Integer> retLst = runningMedianOfThree(orgLst);
      
       System.out.print("\n\nList after calculating median: ");
          
       //ITerating and printing elements
       for(Integer a:retLst)
       {
           System.out.print(a + " ");
       }
   }
  
   //Method that finds the median of three values
   public static List<Integer> runningMedianOfThree(List<Integer> items)
   {
       //Creating a new list
       List<Integer> retLst = new ArrayList<Integer>();
      
       //Adding first two elements
       retLst.add(items.get(0));
       retLst.add(items.get(1));
      
       int median;
      
       //Iterating from third elements
       for(int i=2; i<items.size(); i++)
       {
           //Calculating median
           if ((items.get(i-2) > items.get(i-1)) != (items.get(i-2) > items.get(i)))
           {
               median = items.get(i-2);
           }
           else if ((items.get(i-1) > items.get(i-2)) != (items.get(i-1) > items.get(i)))
           {
               median = items.get(i-1);
           }
           else
           {
               median = items.get(i);
           }
          
           //Adding median value
           retLst.add(median);
       }
      
       //Returning new list
       return retLst;
   }
}

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Sample Run: