Java Program For Deleting A Linked List Node At A Given Position

Given a singly linked list and a position, delete a linked list node at the given position.

Example:

Input: position = 1, Linked List = 8->2->3->1->7
Output: Linked List =  8->3->1->7

Input: position = 0, Linked List = 8->2->3->1->7
Output: Linked List = 2->3->1->7

If the node to be deleted is the root, simply delete it. To delete a middle node, we must have a pointer to the node previous to the node to be deleted. So if positions are not zero, we run a loop position-1 times and get a pointer to the previous node.

Below is the implementation of the above idea.

Java

// A complete working Java program to delete a node in a linked list
// at a given position
class LinkedList
{
    Node head;  // head of list

    /* Linked list Node*/
    class Node
    {
        int data;
        Node next;
        Node(int d)
        {
            data = d;
            next = null;
        }
    }

    /* Inserts a new Node at front of the list. */
    public void push(int new_data)
    {
        /* 1 & 2: Allocate the Node &
                  Put in the data*/
        Node new_node = new Node(new_data);

        /* 3. Make next of new Node as head */
        new_node.next = head;

        /* 4. Move the head to point to new Node */
        head = new_node;
    }

    /* Given a reference (pointer to pointer) to the head of a list
       and a position, deletes the node at the given position */
    void deleteNode(int position)
    {
        // If linked list is empty
        if (head == null)
            return;

        // Store head node
        Node temp = head;

        // If head needs to be removed
        if (position == 0)
        {
            head = temp.next;   // Change head
            return;
        }

        // Find previous node of the node to be deleted
        for (int i=0; temp!=null && i<position-1; i++)
            temp = temp.next;

        // If position is more than number of nodes
        if (temp == null || temp.next == null)
            return;

        // Node temp->next is the node to be deleted
        // Store pointer to the next of node to be deleted
        Node next = temp.next.next;

        temp.next = next;  // Unlink the deleted node from list
    }

    /* This function prints contents of linked list starting from
        the given node */
    public void printList()
    {
        Node tnode = head;
        while (tnode != null)
        {
            System.out.print(tnode.data+" ");
            tnode = tnode.next;
        }
    }

    /* Driver program to test above functions. Ideally this function
       should be in a separate user class.  It is kept here to keep
       code compact */
    public static void main(String[] args)
    {
        /* Start with the empty list */
        LinkedList llist = new LinkedList();

        llist.push(7);
        llist.push(1);
        llist.push(3);
        llist.push(2);
        llist.push(8);

        System.out.println("
Created Linked list is: ");
        llist.printList();

        llist.deleteNode(4);  // Delete node at position 4

        System.out.println("
Linked List after Deletion at position 4: ");
        llist.printList();
    }
}

Output: 

Created Linked List: 
 8  2  3  1  7 
Linked List after Deletion at position 4: 
 8  2  3  1 

Time Complexity: O(n), where n represents the length of the given linked list.
Auxiliary Space: O(1), no extra space is required, so it is a constant.

Please refer complete article on Delete a Linked List node at a given position for more details!