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;
}
}

Answer 1

Program

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.
   
int m = 0;
try {
        m = l.getMin(head, Integer.MAX_VALUE); // store the min in this variable.
}catch(StackOverflowError t) {
        System.out.println("Caught "+t);
}

System.out.println("The smallest is " + m);
}
//method to return minimum element in this list
public int getMin(ListNode head, int min)
{
        if(head==null)
            return min;
        if(head.num < min)
            min = head.num;
        head = head.next;
        return getMin(head, min);
}
}

//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;
   }
}

Output:

Loading my list.
My list is successfully loaded. Please print the smallest element.
Caught java.lang.StackOverflowError
The smallest is 0

Since the linked list is too large hence the output gives StackOverflowError. If you reduce number of nodes then it produce following output.

Output:

Loading my list.
My list is successfully loaded. Please print the smallest element.
The smallest is 17

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