# Linked List | Set 3 (Deleting a node)

We have discussed Linked List Introduction and Linked List Insertion in previous posts on 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 linked list.
To delete a node from linked list, we need to do following steps.
1) Find previous node of the node to be deleted.
2) Change the next of previous node.
3) Free memory for the node to be deleted. ## Recommended: Please solve it on “PRACTICE” first, before moving on to the solution.

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

## C/C++

 `// A complete working C program to demonstrate deletion in singly ` `// linked list ` `#include ` `#include ` ` `  `// A linked list node ` `struct` `Node ` `{ ` `    ``int` `data; ` `    ``struct` `Node *next; ` `}; ` ` `  `/* Given a reference (pointer to pointer) to the head of a list ` `   ``and an int, inserts a new node on the front of the list. */` `void` `push(``struct` `Node** head_ref, ``int` `new_data) ` `{ ` `    ``struct` `Node* new_node = (``struct` `Node*) ``malloc``(``sizeof``(``struct` `Node)); ` `    ``new_node->data  = new_data; ` `    ``new_node->next = (*head_ref); ` `    ``(*head_ref)    = new_node; ` `} ` ` `  `/* Given a reference (pointer to pointer) to the head of a list ` `   ``and a key, deletes the first occurrence of key in linked list */` `void` `deleteNode(``struct` `Node **head_ref, ``int` `key) ` `{ ` `    ``// Store head node ` `    ``struct` `Node* temp = *head_ref, *prev; ` ` `  `    ``// If head node itself holds the key to be deleted ` `    ``if` `(temp != NULL && temp->data == key) ` `    ``{ ` `        ``*head_ref = temp->next;   ``// Changed head ` `        ``free``(temp);               ``// free old head ` `        ``return``; ` `    ``} ` ` `  `    ``// Search for the key to be deleted, keep track of the ` `    ``// previous node as we need to change 'prev->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; ` ` `  `    ``free``(temp);  ``// Free memory ` `} ` ` `  `// This function prints contents of linked list starting from  ` `// the given node ` `void` `printList(``struct` `Node *node) ` `{ ` `    ``while` `(node != NULL) ` `    ``{ ` `        ``printf``(``" %d "``, node->data); ` `        ``node = node->next; ` `    ``} ` `} ` ` `  `/* Drier program to test above functions*/` `int` `main() ` `{ ` `    ``/* Start with the empty list */` `    ``struct` `Node* head = NULL; ` ` `  `    ``push(&head, 7); ` `    ``push(&head, 1); ` `    ``push(&head, 3); ` `    ``push(&head, 2); ` ` `  `    ``puts``(``"Created Linked List: "``); ` `    ``printList(head); ` `    ``deleteNode(&head, 1); ` `    ``puts``(``"\nLinked List after Deletion of 1: "``); ` `    ``printList(head); ` `    ``return` `0; ` `}`

## 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; ` `        ``} ` `    ``} ` ` `  `    ``/* Drier 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(``"\nCreated Linked list is:"``); ` `        ``llist.printList(); ` ` `  `        ``llist.deleteNode(``1``); ``// Delete node at position 4 ` ` `  `        ``System.out.println(``"\nLinked List after Deletion at position 4:"``); ` `        ``llist.printList(); ` `    ``} ` `} `

## Python 3

 `# Python program to delete a node from linked list  ` ` `  `# Node class  ` `class` `Node:  ` ` `  `    ``# Constructor to initialize the node object  ` `    ``def` `__init__(``self``, data):  ` `        ``self``.data ``=` `data  ` `        ``self``.``next` `=` `None` ` `  `class` `LinkedList:  ` ` `  `    ``# Function to initialize head  ` `    ``def` `__init__(``self``):  ` `        ``self``.head ``=` `None` ` `  `    ``# Function to insert a new node at the beginning  ` `    ``def` `push(``self``, new_data):  ` `        ``new_node ``=` `Node(new_data)  ` `        ``new_node.``next` `=` `self``.head  ` `        ``self``.head ``=` `new_node  ` ` `  `    ``# Given a reference to the head of a list and a key,  ` `    ``# delete the first occurence of key in linked list  ` `    ``def` `deleteNode(``self``, key):  ` `         `  `        ``# Store head node  ` `        ``temp ``=` `self``.head  ` ` `  `        ``# If head node itself holds the key to be deleted  ` `        ``if` `(temp ``is` `not` `None``):  ` `            ``if` `(temp.data ``=``=` `key):  ` `                ``self``.head ``=` `temp.``next` `                ``temp ``=` `None` `                ``return` ` `  `        ``# Search for the key to be deleted, keep track of the  ` `        ``# previous node as we need to change 'prev.next'  ` `        ``while``(temp ``is` `not` `None``):  ` `            ``if` `temp.data ``=``=` `key:  ` `                ``break` `            ``prev ``=` `temp  ` `            ``temp ``=` `temp.``next` ` `  `        ``# if key was not present in linked list  ` `        ``if``(temp ``=``=` `None``):  ` `            ``return` ` `  `        ``# Unlink the node from linked list  ` `        ``prev.``next` `=` `temp.``next` ` `  `        ``temp ``=` `None` ` `  ` `  `    ``# Utility function to print the linked LinkedList  ` `    ``def` `printList(``self``):  ` `        ``temp ``=` `self``.head  ` `        ``while``(temp):  ` `            ``print` `(``" %d"` `%``(temp.data)),  ` `            ``temp ``=` `temp.``next` ` `  ` `  `# Driver program  ` `llist ``=` `LinkedList()  ` `llist.push(``7``)  ` `llist.push(``1``)  ` `llist.push(``3``)  ` `llist.push(``2``)  ` ` `  `print` `(``"Created Linked List: "``) ` `llist.printList()  ` `llist.deleteNode(``1``)  ` `print` `(``"\nLinked List after Deletion of 1:"``) ` `llist.printList()  ` ` `  `# This code is contributed by Nikhil Kumar Singh (nickzuck_007)  `

Output:

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

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Improved By : mlv, dkp1903

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