Question

You are given a reference to the head node of a linked list that stores integers. Please print the minimum element in this linked list. The class ListNode.java contains the description of a single node in the linked list. It has a num field to store the integer number and a reference next that points to the next element in the list. The file MyList.class is a pre-defined java code, that creates a linked list. The file ListSmallest.java creates an instance of MyList, and gets the head node of this list. Please fill out the part that says “TODO”, that computes the minimum element in the list. For fun, please solve this problem recursively. This means that no part of your solution may include iterative loops. The list will not contain any integer greater than 2000000.

ListSmallest.java:

public class ListSmallest {

   public static void main(String [] args) {
      
       // Creating an instance of MyList.
       MyList L = new MyList();

       // Get the head of the linked list.
       ListNode head = L.getHead();

       // Create an object of this program to avoid static context.
       ListSmallest l = new ListSmallest();

       // head is the head of my linked list L.
       // TODO: please write a function to print the minimum element in this list. Please store this in the variable m.
       int m = 0; // store the min in this variable.

       System.out.println("The smallest is " + m);
   }
}

ListNode.java:

public class ListNode
{
public int num;
public ListNode next;

public ListNode(int _num, ListNode _next)
{
num = _num;
next = _next;
}
}

MyList.java:

public class MyList
{
private ListNode head;

MyList()
{
System.out.println("Loading my list.");
for (int i = 0; i < 50000; ++i) {
this.head = new ListNode(200000 - i, this.head);
}
this.head = new ListNode(17, this.head);
for (int j = 50000; j < 100000; ++j)
{
this.head = new ListNode(200000 - j, this.head);
}
System.out.println("My list is successfully loaded. Please print the smallest element.");
}

public ListNode getHead()
{
return this.head;
}
}

CANNOT ADJUST NODE SIZE!!

MUST SOLVE RECURSIVELY!!

Answer 1

Adding the code for the class ListSmallest. Created a recursive method findMin which returns the min value of the linked list by the recursive method. Taken the min value: 2000000, as the data cannot be greater than this value.

Added a variable min to hold this largest possible value. If the linked list is null, we return the min value as 2000001 indicating that data is not valid.

Else, we proceed with finding the min value among the given nodes data.

The only change is in this calls ListSmallest. All the other classes remain the same.

public class ListSmallest {

   public int findMin(ListNode head, int min)
   {
      
   if (head == null)

System.out.println("Linked List is empty");
       return min+1;
   if (head.num < min)
       min = head.num;
   else {
       min = findMin(head.next, min);
   }
   return min;
   }
public static void main(String [] args) {
  
// Creating an instance of MyList.
MyList L = new MyList();

// Get the head of the linked list.
ListNode head = L.getHead();

// Create an object of this program to avoid static context.
ListSmallest l = new ListSmallest();

// head is the head of my linked list L.
// function to print the minimum element in this list. storing this in the variable m.
int min = 2000000;//taking the largest possible value
int m = l.findMin(head, min); // store the min in this variable.

System.out.println("The smallest is " + m);
}
}