Delete 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->7Input: 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++14
// A complete working C++ program to delete// a node in a linked list at a given position#include <iostream>using namespace std;// A linked list nodeclass Node {public: int data; 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(Node** head_ref, int new_data){ Node* new_node = new 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 positionvoid deleteNode(Node** head_ref, int position){ // If linked list is empty if (*head_ref == NULL) return; // Store head node Node* temp = *head_ref; // If head needs to be removed if (position == 0) { // Change head *head_ref = temp->next; // Free old head free(temp); 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 node from linked list free(temp->next); // Free memory // Unlink the deleted node from list temp->next = next;}// This function prints contents of linked// list starting from the given nodevoid printList(Node* node){ while (node != NULL) { cout << node->data << " "; node = node->next; }}// Driver codeint main(){ // Start with the empty list Node* head = NULL; push(&head, 7); push(&head, 1); push(&head, 3); push(&head, 2); push(&head, 8); cout << "Created Linked List: "; printList(head); deleteNode(&head, 4); cout << "\nLinked List after Deletion at position 4: "; printList(head); return 0;}// This code is contributed by premsai2030 |
C
// Simple C code to delete node at particular position#include <stdio.h>#include <stdlib.h>void insert(int);void display_List();void delete (int);struct node // Structure declaration{ int data; struct node* next; // Self referral pointer}* head = NULL, *tail = NULL; // Initial value of Head and Tail pointer is NULLvoid delete (int pos){ struct node* temp = head; // Creating a temporary // variable pointing to head int i; if (pos == 0) { printf("\nElement deleted is : %d\n", temp->data); head = head->next; // Advancing the head pointer temp->next = NULL; free(temp); // Node is deleted } else { for (i = 0; i < pos - 1; i++) { temp = temp->next; } // Now temp pointer points to the previous node of // the node to be deleted struct node* del = temp->next; // del pointer points to the node // to be deleted temp->next = temp->next->next; printf("\nElement deleted is : %d\n", del->data); del->next = NULL; free(del); // Node is deleted } printf("\nUpdated Linked List is : \n"); display_List(); return;}void insert(int value){ struct node* newnode; // Creating a new node newnode = (struct node*)malloc( sizeof(struct node)); // Allocating dynamic memory newnode->data = value; // Assigning value to newnode newnode->next = NULL; if (head == NULL) // Checking if List is empty { head = newnode; tail = newnode; } else // If not empty then... { tail->next = newnode; tail = newnode; // Updating the tail node with each // insertion } return;}void display_List(){ struct node* temp; // Creating a temporary pointer to // the structure temp = head; // temp points to head; while (temp != NULL) { if (temp->next == NULL) { printf(" %d->NULL", temp->data); } else { printf(" %d->", temp->data); } temp = temp->next; // Traversing the List till end } printf("\n"); return;}// --Driver Code--int main(){ insert(10); insert(20); insert(30); insert(40); insert(50); insert(60); printf("\n--Created Linked List--\n"); display_List(); printf("\nLinked List after deletion at position 0"); delete (0); // List indexing starts from 0 printf("\nLinked List after deletion at position 2"); delete (2); return 0;}// This code is contributed by Sanjeeban Mukhopadhyay. |
Java
// A complete working Java program to delete a node in a// linked list at a given positionclass 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(); }} |
Python3
# Python program to delete a node in a linked list# at a given position# Node classclass Node: # Constructor to initialize the node object def __init__(self, data): self.data = data self.next = Noneclass 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 # This delete function code is contributed by Arabin Islam def deleteNodeAtGivenPosition(self, position): if self.head is None: return index = 0 current = self.head while current.next and index < position: previous = current current = current.next index += 1 if index < position: print("\nIndex is out of range.") elif index == 0: self.head = self.head.next else: previous.next = current.next # current = None #Optional statement # Utility function to print the LinkedList def printList(self): temp = self.head while(temp): print(" %d " % (temp.data), end=" ") temp = temp.next# Driver program to test above functionllist = LinkedList()llist.push(7)llist.push(1)llist.push(3)llist.push(2)llist.push(8)print("Created Linked List: ")llist.printList()llist.deleteNodeAtGivenPosition(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 positionusing 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 |
Javascript
<script>// A complete working javascript program to// delete a node in a linked list at a// given position// head of listvar head;/* Linked list Node */class Node{ constructor(val) { this.data = val; this.next = null; }}/* Inserts a new Node at front of the list. */function push(new_data){ /* * 1 & 2: Allocate the Node & Put in the data */ var 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 */function deleteNode(position){ // If linked list is empty if (head == null) return; // Store head node var 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(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 var 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*/function printList(){ var tnode = head; while (tnode != null) { document.write(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*//* Start with the empty list */push(7);push(1);push(3);push(2);push(8);document.write("Created Linked list is: <br/>");printList();// Delete node at position 4deleteNode(4);document.write("<br/>Linked List after " + "Deletion at position 4: <br/>");printList();// This code is contributed by todaysgaurav</script> |
Output
Created Linked List: 8 2 3 1 7 Linked List after Deletion at position 4: 8 2 3 7
Complexity Analysis :
- Best Case : O(1) if given position is 1
- Average & Worst Case : O(N) if position given is size-1 then need to traverse till position not found.
- Space Complexity : O(1) no extra any space is required
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