Java Program For Deleting A Node In A Linked List

We have discussed Linked List Introduction and Linked List Insertion in previous posts on a singly linked list.
Let us formulate the problem statement to understand the deletion process. Given a ‘key’, delete the first occurrence of this key in the linked list. 

Iterative Method:
To delete a node from the linked list, we need to do the following steps. 
1) Find the previous node of the node to be deleted. 
2) Change the next of the previous node. 
3) Free memory for the node to be deleted.

Since every node of the linked list is dynamically allocated using malloc() in C, we need to call free() for freeing memory allocated for the node to be deleted.

Java

// A complete working Java program
// to demonstrate deletion
// in singly linked list
class LinkedList {
    Node head; // head of list

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

    /* Given a key, deletes the first
       occurrence of key in
     * linked list */
    void deleteNode(int key)
    {
        // Store head node
        Node temp = head, prev = null;

        // If head node itself holds the key to be deleted
        if (temp != null && temp.data == key) {
            head = temp.next; // Changed head
            return;
        }

        // Search for the key to be deleted, keep track of
        // the previous node as we need to change temp.next
        while (temp != null && temp.data != key) {
            prev = temp;
            temp = temp.next;
        }

        // If key was not present in linked list
        if (temp == null)
            return;

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

    /* Inserts a new Node at front of the list. */
    public void push(int new_data)
    {
        Node new_node = new Node(new_data);
        new_node.next = head;
        head = new_node;
    }

    /* 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)
    {
        LinkedList llist = new LinkedList();

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

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

        llist.deleteNode(1); // Delete node with data 1

        System.out.println(
            "
Linked List after Deletion of 1:");
        llist.printList();
    }
}

Output:

Created Linked List: 
 2  3  1  7 
Linked List after Deletion of 1: 
 2  3  7

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 Linked List | Set 3 (Deleting a node) for more details!