Question

JAVA - Write a recursive function that takes a linked list as input and returns all of the elements in the linked list.

Input: 1, 2, 3, 4, 5

Output: (1+2+3+4+5)/5 = 3

What I have:

public static int findMean (Node head, Node cur, int n){

int average = 0;

if (head == null){

if(n == 0)

return 0;

}

if (n > 0){

int sum = n + findMean(head, head.next, n -1);

average = (sum)/n;

}

return average;

}

In the main method:

System.out.println("Average is "+ findMean(head, head.next, 5));

//Should be 3 but gives me 1

Answer 1

Two methods have been provided considering the following facts:

1) If the call given in the question is to be used.

2) If the call given in the question can be changed.

Method code screenshots:

Method code:

     //Define the method findMean().

     public static int findMean (Node head, Node cur, int n)

     {

         

          //If the head is

          //null then return 0.

          if (head == null)

          {

              return 0;

          }

         

          //Otherwise if the head is pointing

          //to the last element in the list

          //then, return the value of the head.

          else if (head.next == null)

          {

              return head.item;

          }

         

          //Otherwise, recursively call

          //the method to calculate the sum.

          else

          {

             

              int sum = head.item + (findMean(head.next, cur, n-1));

             

              if (head.next == cur)

              {

                   return (head.item + sum)/n;

              }

              else

              {

                   return sum;

              }

          }

     }

Below is the code to test the above given method.

Code Screenshots:

Sample Output:

Code To Copy:

//Define the class Node.

class Node

{

     //Declare the required

     //data members.

     int item;

     Node next;

    

     Node(int d)

     {

          item = d;

          next = null;

     }

}

//Define the class Main.

public class Main {

    

     // Define the main() method.

     public static void main(String args[])

     {

          //Define a linked list.

          Node head = new Node(1);

          head.next = new Node(5);

          head.next.next = new Node(3);

          head.next.next.next = new Node(4);

          head.next.next.next.next = new Node(2);

         

          //Call the method and display the average.

          System.out.println("Average is "+ findMean(head, head.next, 5));

     }

    

     //Define the method findMean().

     public static int findMean (Node head, Node cur, int n)

     {

         

          //If the head is

          //null then return 0.

          if (head == null)

          {

              return 0;

          }

         

          //Otherwise if the head is pointing

          //to the last element in the list

          //then, return the value of the head.

          else if (head.next == null)

          {

              return head.item;

          }

         

          //Otherwise, recursively call

          //the method to calculate the sum.

          else

          {

             

              int sum = head.item + (findMean(head.next, cur, n-1));

             

              if (head.next == cur)

              {

                   return (head.item + sum)/n;

              }

              else

              {

                   return sum;

              }

          }

     }

}

Alt version (If the call to the method can be changed):

Method code screenshots:

Method code:

     public static int findMean (Node head, Node cur, int n)

     {

          if (head == null)

          {

              return 0;

          }

          else if (cur.next == null){

              return cur.item;

          }

          else

          {

              int sum = cur.item + (findMean(head, cur.next, n-1));

              if (head == cur)

              {

                   return sum/n;

              }

              else

              {

                   return sum;

              }

          }

     }

Below is the code to test the above given method.

Code Screenshots:

Sample Output:

Code To Copy:

//Define the class Node.

class Node

{

     //Declare the required

     //data members.

     int item;

     Node next;

    

     Node(int d)

     {

          item = d;

          next = null;

     }

}

public class Main {

    

    

     public static void main(String args[])

     {

          Node head = new Node(1);

          head.next = new Node(5);

          head.next.next = new Node(3);

          head.next.next.next = new Node(4);

          head.next.next.next.next = new Node(2);

          System.out.println("Average is "+ findMean(head, head, 5));

     }

    

     public static int findMean (Node head, Node cur, int n)

     {

          if (head == null)

          {

              return 0;

          }

          else if (cur.next == null){

              return cur.item;

          }

          else

          {

              int sum = cur.item + (findMean(head, cur.next, n-1));

              if (head == cur)

              {

                   return sum/n;

              }

              else

              {

                   return sum;

              }

          }

     }

}