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.
C
// A complete working C program to delete a node in a linked list // at a given position #include <stdio.h> #include <stdlib.h> // 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 position, deletes the node at the given position */ void deleteNode( struct Node **head_ref, int position) { // If linked list is empty if (*head_ref == NULL) return ; // Store head node struct Node* temp = *head_ref; // If head needs to be removed if (position == 0) { *head_ref = temp->next; // Change head free (temp); // free old 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 struct Node *next = temp->next->next; // Unlink the node from linked list free (temp->next); // Free memory temp->next = next; // Unlink the deleted node from list } // 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; } } /* Driver 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); push(&head, 8); puts ( "Created Linked List: " ); printList(head); deleteNode(&head, 4); puts ( "\nLinked List after Deletion at position 4: " ); printList(head); return 0; } |
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( "\nCreated Linked list is: " ); llist.printList(); llist.deleteNode( 4 ); // Delete node at position 4 System.out.println( "\nLinked List after Deletion at position 4: " ); llist.printList(); } } |
Python
# Python program to delete a node in a linked list # at a given position # Node class class Node: # Constructor to initialize the node object def __init__( self , data): self .data = data self . next = None class LinkedList: # Constructor 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 position, delete the node at a given position def deleteNode( self , position): # If linked list is empty if self .head = = None : return # Store head node temp = self .head # If head needs to be removed if position = = 0 : self .head = temp. next temp = None return # Find previous node of the node to be deleted for i in range (position - 1 ): temp = temp. next if temp is None : break # If position is more than number of nodes if temp is None : return if temp. next is None : return # Node temp.next is the node to be deleted # store pointer to the next of node to be deleted next = temp. next . next # Unlink the node from linked list temp. next = None temp. next = next # Utility function to print the linked LinkedList def printList( self ): temp = self .head while (temp): print " %d " % (temp.data), temp = temp. next # Driver program to test above function llist = LinkedList() llist.push( 7 ) llist.push( 1 ) llist.push( 3 ) llist.push( 2 ) llist.push( 8 ) print "Created Linked List: " llist.printList() llist.deleteNode( 4 ) print "\nLinked List after Deletion at position 4: " llist.printList() # This code is contributed by Nikhil Kumar Singh(nickzuck_007) |
C#
// A complete working C# program to delete // a node in a linked list at a given position using System; class GFG{ // Head of list Node head; // Linked list Node public class Node { public int data; public Node next; public 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) { // Change head head = temp.next; 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; // Unlink the deleted node from list temp.next = next; } // This function prints contents of // linked list starting from the // given node public void printList() { Node tnode = head; while (tnode != null ) { Console.Write(tnode.data + " " ); tnode = tnode.next; } } // Driver code public static void Main(String[] args) { // Start with the empty list GFG llist = new GFG(); llist.Push(7); llist.Push(1); llist.Push(3); llist.Push(2); llist.Push(8); Console.WriteLine( "\nCreated Linked list is: " ); llist.printList(); // Delete node at position 4 llist.deleteNode(4); Console.WriteLine( "\nLinked List after " + "Deletion at position 4: " ); llist.printList(); } } // This code is contributed by Rajput-Ji |
Output:
Created Linked List: 8 2 3 1 7 Linked List after Deletion at position 4: 8 2 3 1
Thanks to Hemanth Kumar for suggesting initial solution. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above
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