Circular Doubly Linked List - Traversal
Traversing through a circular doubly linked list is very easy. It requires creating a temp node pointing to the head of the list. If the temp node is not null, display its content and move to the next node using temp next. Repeat the process till the temp node reaches the starting node (head of the list). If the temp node is empty at the start, then the list contains no item.
A circular doubly linked list can be traversed from any node as the starting point. Traverse the list till reaches the same node.
The function PrintList is created for this purpose. It is a 3-step process.
void PrintList() { //1. create a temp node pointing to head Node* temp = head; //2. if the temp node is not null continue // displaying the content and move to the // next node till the temp becomes head if(temp != NULL) { cout<<"The list contains: "; while(true) { cout<<temp->data<<" "; temp = temp->next; if(temp == head) break; } cout<<"\n"; } else { //3. If the temp node is null at the start, // the list is empty cout<<"The list is empty.\n"; } }
void PrintList(struct Node* head_ref) { //1. create a temp node pointing to head struct Node* temp = head_ref; //2. if the temp node is not null continue // displaying the content and move to the // next node till the temp becomes head 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 { //3. If the temp node is null at the start, // the list is empty printf("The list is empty.\n"); } }
def PrintList(self): #1. create a temp node pointing to head temp = self.head #2. if the temp node is not null continue # displaying the content and move to the # next node till the temp becomes 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: #3. If the temp node is null at the start, # the list is empty print("The list is empty.")
void PrintList() { //1. create a temp node pointing to head Node temp = new Node(); temp = this.head; //2. if the temp node is not null continue // displaying the content and move to the // next node till the temp becomes 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.print(); } else { //3. If the temp node is null at the start, // the list is empty System.out.println("The list is empty."); } }
public void PrintList() { //1. create a temp node pointing to head Node temp = new Node(); temp = this.head; //2. if the temp node is not null continue // displaying the content and move to the // next node till the temp becomes 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 { //3. If the temp node is null at the start, // the list is empty Console.WriteLine("The list is empty."); } }
public function PrintList() { //1. create a temp node pointing to head $temp = new Node(); $temp = $this->head; //2. if the temp node is not null continue // displaying the content and move to the // next node till the temp becomes head if($temp != null) { echo "The list contains: "; while(true) { echo $temp->data." "; $temp = $temp->next; if($temp == $this->head) break; } echo "\n"; } else { //3. If the temp node is null at the start, // the list is empty echo "The list is empty.\n"; } }
The below is a complete program that uses above discussed concept to traverse through the circular doubly linked list and displaying its content.
#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; } } //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); //traverse to display the content of the list. MyList.PrintList(); return 0; }
The above code will give the following output:
The list contains: 10 20 30
#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; } } //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); //traverse to display the content of the list. PrintList(MyList); return 0; }
The above code will give the following output:
The list contains: 10 20 30
# 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 #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) #traverse to display the content of the list. MyList.PrintList()
The above code will give the following output:
The list contains: 10 20 30
//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; } } //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); //traverse to display the content of the list. MyList.PrintList(); } }
The above code will give the following output:
The list contains: 10 20 30
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; } } //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); //traverse to display the content of the list. MyList.PrintList(); } }
The above code will give the following output:
The list contains: 10 20 30
<?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; } } //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); //traverse to display the content of the list. $MyList->PrintList(); ?>
The above code will give the following output:
The list contains: 10 20 30