Circular Doubly Linked List - Delete the first node
In this method, the first node of the circular doubly 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 circular doubly linked list is very easy. If the list contains one node, delete the node. If the list contains more than one node, then create two nodes - temp and firstNode both pointing to the head. Using temp node, traverse to the last node of the list. Make next of head as the head node and update all links. Finally, delete the first node.
The function pop_front is created for this purpose. It is a 4-step process.
void pop_front() { if(head != NULL) { //1. the list contains one node, delete // make the head null if(head->next == head) { head = NULL; } else { //2. if the list contains more than one node, // create two nodes - temp and firstNode, both // pointing to head node Node* temp = head; Node* firstNode = head; //3. using temp node, traverse to the last node while(temp->next != head) { temp = temp->next; } //4. Make head as next of head, and // update links head = head->next; head->prev = temp; temp->next = head; free(firstNode); } } }
void pop_front(struct Node** head_ref) { if(*head_ref != NULL) { //1. the list contains one node, delete // make the head null if((*head_ref)->next == *head_ref) { *head_ref = NULL; } else { //2. if the list contains more than one node, // create two nodes - temp and firstNode, both // pointing to head node struct Node* temp = *head_ref; struct Node* firstNode = *head_ref; //3. using temp node, traverse to the last node while(temp->next != *head_ref) { temp = temp->next; } //4. Make head as next of head, and // update links *head_ref = (*head_ref)->next; (*head_ref)->prev = temp; temp->next = *head_ref; free(firstNode); } } }
def pop_front(self): if(self.head != None): #1. the list contains one node, delete # make the head null if(self.head.next == self.head): self.head = None else: #2. if the list contains more than one node, # create two nodes - temp and firstNode, both # pointing to head node temp = self.head firstNode = self.head #3. using temp node, traverse to the last node while(temp.next != self.head): temp = temp.next #4. Make head as next of head, and # update links self.head = self.head.next self.head.prev = temp temp.next = self.head firstNode = None
void pop_front() { if(this.head != null) { //1. the list contains one node, delete // make the head null if(this.head.next == this.head) { this.head = null; } else { //2. if the list contains more than one node, // create two nodes - temp and firstNode, both // pointing to head node Node temp = this.head; Node firstNode = this.head; //3. using temp node, traverse to the last node while(temp.next != this.head) { temp = temp.next; } //4. Make head as next of head, and // update links this.head = this.head.next; this.head.prev = temp; temp.next = this.head; firstNode = null; } } }
public void pop_front() { if(this.head != null) { //1. the list contains one node, delete // make the head null if(this.head.next == this.head) { this.head = null; } else { //2. if the list contains more than one node, // create two nodes - temp and firstNode, both // pointing to head node Node temp = this.head; Node firstNode = this.head; //3. using temp node, traverse to the last node while(temp.next != this.head) { temp = temp.next; } //4. Make head as next of head, and // update links this.head = this.head.next; this.head.prev = temp; temp.next = this.head; firstNode = null; } } }
public function pop_front() { if($this->head != null) { //1. the list contains one node, delete // make the head null if($this->head->next == $this->head) { $this->head = null; } else { //2. if the list contains more than one node, // create two nodes - temp and firstNode, both // pointing to head node $temp = $this->head; $firstNode = $this->head; //3. using temp node, traverse to the last node while($temp->next != $this->head) { $temp = $temp->next; } //4. Make head as next of head, and // update links $this->head = $this->head->next; $this->head->prev = $temp; $temp->next = $this->head; $firstNode = null; } } }
The below is a complete program that uses above discussed concept of deleting the first node of the circular doubly linked list.
#include <iostream> using namespace std; //node structure struct Node { int data; Node* next; Node* prev; }; 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; newNode->prev = NULL; if(head == NULL) { head = newNode; newNode->next = head; newNode->prev = head; } else { Node* temp = head; while(temp->next != head) temp = temp->next; temp->next = newNode; newNode->next = head; newNode->prev = temp; head->prev = newNode; } } //Delete first node of the list void pop_front() { if(head != NULL) { if(head->next == head) { head = NULL; } else { Node* temp = head; Node* firstNode = head; while(temp->next != head) { temp = temp->next; } head = head->next; head->prev = temp; temp->next = head; free(firstNode); } } } //display the content of the list void PrintList() { Node* temp = head; if(temp != NULL) { cout<<"The list contains: "; while(true) { cout<<temp->data<<" "; temp = temp->next; if(temp == head) break; } cout<<endl; } else { cout<<"The list is empty.\n"; } } }; // test the code int main() { LinkedList MyList; //Add three elements at the end of 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; struct Node* prev; }; //Add new element at the end of the list void push_back(struct Node** head_ref, int newElement) { struct Node *newNode, *temp; newNode = (struct Node*)malloc(sizeof(struct Node)); newNode->data = newElement; newNode->next = NULL; newNode->prev = NULL; if(*head_ref == NULL) { *head_ref = newNode; newNode->next = *head_ref; newNode->prev = *head_ref; } else { temp = *head_ref; while(temp->next != *head_ref) { temp = temp->next; } temp->next = newNode; newNode->next = *head_ref; newNode->prev = temp; (*head_ref)->prev = newNode; } } //Delete first node of the list void pop_front(struct Node** head_ref) { if(*head_ref != NULL) { if((*head_ref)->next == *head_ref) { *head_ref = NULL; } else { struct Node* temp = *head_ref; struct Node* firstNode = *head_ref; while(temp->next != *head_ref) { temp = temp->next; } *head_ref = (*head_ref)->next; (*head_ref)->prev = temp; temp->next = *head_ref; free(firstNode); } } } //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 (1) { printf("%i ",temp->data); temp = temp->next; if(temp == head_ref) break; } printf("\n"); } else { printf("The list is empty.\n"); } } // test the code int main() { struct Node* MyList = NULL; //Add three elements at the end of 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 self.prev = None #class Linked List 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 newNode.next = self.head newNode.prev = self.head return else: temp = self.head while(temp.next != self.head): temp = temp.next temp.next = newNode newNode.next = self.head newNode.prev = temp self.head.prev = newNode #Delete first node of the list def pop_front(self): if(self.head != None): if(self.head.next == self.head): self.head = None else: temp = self.head firstNode = self.head while(temp.next != self.head): temp = temp.next self.head = self.head.next self.head.prev = temp temp.next = self.head firstNode = None #display the content of the list def PrintList(self): temp = self.head if(temp != None): print("The list contains:", end=" ") while (True): print(temp.data, end=" ") temp = temp.next if(temp == self.head): break print() else: print("The list is empty.") # test the code MyList = LinkedList() #Add three elements at the end of 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; Node prev; }; 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; newNode.next = null; if(head == null) { head = newNode; newNode.next = head; newNode.prev = head; } else { Node temp = new Node(); temp = head; while(temp.next != head) temp = temp.next; temp.next = newNode; newNode.next = head; newNode.prev = temp; head.prev = newNode; } } //Delete first node of the list void pop_front() { if(this.head != null) { if(this.head.next == this.head) { this.head = null; } else { Node temp = this.head; Node firstNode = this.head; while(temp.next != this.head) { temp = temp.next; } this.head = this.head.next; this.head.prev = temp; temp.next = this.head; firstNode = 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(true) { System.out.print(temp.data + " "); temp = temp.next; if(temp == this.head) break; } 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 three elements at the end of 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; public Node prev; }; 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; newNode.prev = null; if(head == null) { head = newNode; newNode.next = head; newNode.prev = head; } else { Node temp = new Node(); temp = head; while(temp.next != head) temp = temp.next; temp.next = newNode; newNode.next = head; newNode.prev = temp; head.prev = newNode; } } //Delete first node of the list public void pop_front() { if(this.head != null) { if(this.head.next == this.head) { this.head = null; } else { Node temp = this.head; Node firstNode = this.head; while(temp.next != this.head) { temp = temp.next; } this.head = this.head.next; this.head.prev = temp; temp.next = this.head; firstNode = 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(true) { Console.Write(temp.data + " "); temp = temp.next; if(temp == this.head) break; } Console.WriteLine(); } else { Console.WriteLine("The list is empty."); } } }; // test the code class Implementation { static void Main(string[] args) { LinkedList MyList = new LinkedList(); //Add three elements at the end of 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; public $prev; } 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; $newNode->prev = null; if($this->head == null) { $this->head = $newNode; $newNode->next = $this->head; } else { $temp = new Node(); $temp = $this->head; while($temp->next !== $this->head) { $temp = $temp->next; } $temp->next = $newNode; $newNode->next = $this->head; $newNode->prev = $temp; $this->head->prev = $newNode; } } //Delete first node of the list public function pop_front() { if($this->head != null) { if($this->head->next == $this->head) { $this->head = null; } else { $temp = $this->head; $firstNode = $this->head; while($temp->next != $this->head) { $temp = $temp->next; } $this->head = $this->head->next; $this->head->prev = $temp; $temp->next = $this->head; $firstNode = null; } } } //display the content of the list public function PrintList() { $temp = new Node(); $temp = $this->head; if($temp != null) { echo "The list contains: "; while(true) { echo $temp->data." "; $temp = $temp->next; if($temp == $this->head) break; } echo "\n"; } else { echo "The list is empty.\n"; } } }; // test the code $MyList = new LinkedList(); //Add three elements at the end of 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