Linked List - Delete the first node
In this method, the first node of the linked list is deleted. For example - if the given list is 10->20->30->40 and the first node is deleted, the list becomes 20->30->40.
Deleting the first node of the linked list is very easy. If the head is not null then create a temp node pointing to head and move head to the next of head. Then delete the temp node.
The function pop_front is created for this purpose. It is a 3-step process.
void pop_front() { if(head != NULL) { //1. if head is not null, create a // temp node pointing to head Node* temp = head; //2. move head to next of head head = head->next; //3. delete temp node free(temp); } }
void pop_front(struct Node** head_ref) { if(*head_ref != NULL) { //1. if head is not null, create a // temp node pointing to head struct Node *temp = *head_ref; //2. move head to next of head *head_ref = (*head_ref)->next; //3. delete temp node temp = NULL; } }
def pop_front(self): if(self.head != None): #1. if head is not null, create a # temp node pointing to head temp = self.head #2. move head to next of head self.head = self.head.next #3. delete temp node temp = None
void pop_front() { if(this.head != null) { //1. if head is not null, create a // temp node pointing to head Node temp = this.head; //2. move head to next of head this.head = this.head.next; //3. delete temp node temp = null; } }
public void pop_front() { if(this.head != null) { //1. if head is not null, create a // temp node pointing to head Node temp = this.head; //2. move head to next of head this.head = this.head.next; //3. delete temp node temp = null; } }
public function pop_front() { if($this->head != null) { //1. if head is not null, create a // temp node pointing to head $temp = $this->head; //2. move head to next of head $this->head = $this->head->next; //3. delete temp node $temp = null; } }
The below is a complete program that uses above discussed concept of deleting the first node of the linked list.
#include <iostream> using namespace std; //node structure struct Node { int data; Node* next; }; class LinkedList { private: Node* head; public: LinkedList(){ head = NULL; } //Add new element at the end of the list void push_back(int newElement) { Node* newNode = new Node(); newNode->data = newElement; newNode->next = NULL; if(head == NULL) { head = newNode; } else { Node* temp = head; while(temp->next != NULL) temp = temp->next; temp->next = newNode; } } //Delete first node of the list void pop_front() { if(head != NULL) { Node* temp = head; head = head->next; free(temp); } } //display the content of the list void PrintList() { Node* temp = head; if(temp != NULL) { cout<<"The list contains: "; while(temp != NULL) { cout<<temp->data<<" "; temp = temp->next; } cout<<"\n"; } else { cout<<"The list is empty.\n"; } } }; // test the code int main() { LinkedList MyList; //Add four elements in the list. MyList.push_back(10); MyList.push_back(20); MyList.push_back(30); MyList.push_back(40); MyList.PrintList(); //Delete the first node MyList.pop_front(); MyList.PrintList(); return 0; }
The above code will give the following output:
The list contains: 10 20 30 40 The list contains: 20 30 40
#include <stdio.h> #include <stdlib.h> //node structure struct Node { int data; struct Node* next; }; //Add new element at the end of the list void push_back(struct Node** n, int newElement) { struct Node *newNode, *temp; newNode = (struct Node*)malloc(sizeof(struct Node)); newNode->data = newElement; newNode->next = NULL; if(*n == NULL) { *n = newNode; } else { temp = *n; while(temp->next != NULL) { temp = temp->next; } temp->next = newNode; } } //Delete first node of the list void pop_front(struct Node** head_ref) { if(*head_ref != NULL) { struct Node *temp = *head_ref; *head_ref = (*head_ref)->next; temp = NULL; } } //display the content of the list void PrintList(struct Node* head_ref) { struct Node* temp = head_ref; if(head_ref != NULL) { printf("The list contains: "); while (temp != NULL) { printf("%i ",temp->data); temp = temp->next; } printf("\n"); } else { printf("The list is empty.\n"); } } // test the code int main() { struct Node* MyList = NULL; //Add four elements in the list. push_back(&MyList, 10); push_back(&MyList, 20); push_back(&MyList, 30); push_back(&MyList, 40); PrintList(MyList); //Delete the first node pop_front(&MyList); PrintList(MyList); return 0; }
The above code will give the following output:
The list contains: 10 20 30 40 The list contains: 20 30 40
# node structure class Node: def __init__(self, data): self.data = data self.next = None #class LinkedList class LinkedList: def __init__(self): self.head = None #Add new element at the end of the list def push_back(self, newElement): newNode = Node(newElement) if(self.head == None): self.head = newNode return else: temp = self.head while(temp.next != None): temp = temp.next temp.next = newNode #Delete first node of the list def pop_front(self): if(self.head != None): temp = self.head self.head = self.head.next temp = None #display the content of the list def PrintList(self): temp = self.head if(temp != None): print("The list contains:", end=" ") while (temp != None): print(temp.data, end=" ") temp = temp.next print() else: print("The list is empty.") # test the code MyList = LinkedList() #Add four elements in the list. MyList.push_back(10) MyList.push_back(20) MyList.push_back(30) MyList.push_back(40) MyList.PrintList() #Delete the first node MyList.pop_front() MyList.PrintList()
The above code will give the following output:
The list contains: 10 20 30 40 The list contains: 20 30 40
//node structure class Node { int data; Node next; }; class LinkedList { Node head; LinkedList(){ head = null; } //Add new element at the end of the list void push_back(int newElement) { Node newNode = new Node(); newNode.data = newElement; newNode.next = null; if(head == null) { head = newNode; } else { Node temp = new Node(); temp = head; while(temp.next != null) temp = temp.next; temp.next = newNode; } } //Delete first node of the list void pop_front() { if(this.head != null) { Node temp = this.head; this.head = this.head.next; temp = null; } } //display the content of the list void PrintList() { Node temp = new Node(); temp = this.head; if(temp != null) { System.out.print("The list contains: "); while(temp != null) { System.out.print(temp.data + " "); temp = temp.next; } System.out.println(); } else { System.out.println("The list is empty."); } } }; // test the code public class Implementation { public static void main(String[] args) { LinkedList MyList = new LinkedList(); //Add four elements in the list. MyList.push_back(10); MyList.push_back(20); MyList.push_back(30); MyList.push_back(40); MyList.PrintList(); //Delete the first node MyList.pop_front(); MyList.PrintList(); } }
The above code will give the following output:
The list contains: 10 20 30 40 The list contains: 20 30 40
using System; //node structure class Node { public int data; public Node next; }; class LinkedList { Node head; public LinkedList(){ head = null; } //Add new element at the end of the list public void push_back(int newElement) { Node newNode = new Node(); newNode.data = newElement; newNode.next = null; if(head == null) { head = newNode; } else { Node temp = new Node(); temp = head; while(temp.next != null) temp = temp.next; temp.next = newNode; } } //Delete first node of the list public void pop_front() { if(this.head != null) { Node temp = this.head; this.head = this.head.next; temp = null; } } //display the content of the list public void PrintList() { Node temp = new Node(); temp = this.head; if(temp != null) { Console.Write("The list contains: "); while(temp != null) { Console.Write(temp.data + " "); temp = temp.next; } Console.WriteLine(); } else { Console.WriteLine("The list is empty."); } } }; // test the code class Implementation { static void Main(string[] args) { LinkedList MyList = new LinkedList(); //Add four elements in the list. MyList.push_back(10); MyList.push_back(20); MyList.push_back(30); MyList.push_back(40); MyList.PrintList(); //Delete the first node MyList.pop_front(); MyList.PrintList(); } }
The above code will give the following output:
The list contains: 10 20 30 40 The list contains: 20 30 40
<?php //node structure class Node { public $data; public $next; } class LinkedList { public $head; public function __construct(){ $this->head = null; } //Add new element at the end of the list public function push_back($newElement) { $newNode = new Node(); $newNode->data = $newElement; $newNode->next = null; if($this->head == null) { $this->head = $newNode; } else { $temp = new Node(); $temp = $this->head; while($temp->next != null) { $temp = $temp->next; } $temp->next = $newNode; } } //Delete first node of the list public function pop_front() { if($this->head != null) { $temp = $this->head; $this->head = $this->head->next; $temp = null; } } //display the content of the list public function PrintList() { $temp = new Node(); $temp = $this->head; if($temp != null) { echo "The list contains: "; while($temp != null) { echo $temp->data." "; $temp = $temp->next; } echo "\n"; } else { echo "The list is empty.\n"; } } }; // test the code $MyList = new LinkedList(); //Add four elements in the list. $MyList->push_back(10); $MyList->push_back(20); $MyList->push_back(30); $MyList->push_back(40); $MyList->PrintList(); //Delete the first node $MyList->pop_front(); $MyList->PrintList(); ?>
The above code will give the following output:
The list contains: 10 20 30 40 The list contains: 20 30 40