# Circular Doubly Linked List - Delete all nodes

Deleting all nodes of a circular doubly linked list requires traverse through the list and deleting each node one by one. It requires creating a current node pointing to the next of head. Delete the current node and move to the next node using temp node. Repeat the process till the current node becomes head. At last, delete the head.

The function deleteAllNodes is created for this purpose. It is a 3-step process.

```void deleteAllNodes() {

//1. if head is not null create a temp node
//   and current node pointed to next of head
Node *temp, *current;

//2. if current node is not equal to head, delete the
//   current node and move current to next node using temp,
//   repeat the process till the current reaches the head
temp = current->next;
free(current);
current = temp;
}

}
cout<<"All nodes are deleted successfully.\n";
}
```
```void deleteAllNodes(struct Node** head_ref) {

//1. if head is not null create a temp node
//   and current node pointed to next of head
struct Node *temp, *current;

//2. if current node is not equal to head, delete the
//   current node and move current to next node using temp,
//   repeat the process till the current reaches the head
temp = current->next;
free(current);
current = temp;
}

}
printf("All nodes are deleted successfully.\n");
}
```
```def deleteAllNodes(self):

#1. if head is not null create a temp node
#   and current node pointed to next of head

#2. if current node is not equal to head, delete the
#   current node and move current to next node using temp,
#   repeat the process till the current reaches the head
temp = current.next
current = None
current = temp

print("All nodes are deleted successfully.")
```
```void deleteAllNodes() {

//1. if head is not null create a temp node
//   and current node pointed to next of head
Node temp = new Node();
Node current = new Node();

//2. if current node is not equal to head, delete the
//   current node and move current to next node using temp,
//   repeat the process till the current reaches the head
temp = current.next;
current = null;
current = temp;
}

}
System.out.println("All nodes are deleted successfully.");
}
```
```public void deleteAllNodes() {

//1. if head is not null create a temp node
//   and current node pointed to next of head
Node temp = new Node();
Node current = new Node();

//2. if current node is not equal to head, delete the
//   current node and move current to next node using temp,
//   repeat the process till the current reaches the head
temp = current.next;
current = null;
current = temp;
}

}
Console.WriteLine("All nodes are deleted successfully.");
}
```
```public function deleteAllNodes() {

//1. if head is not null create a temp node
//   and current node pointed to next of head
\$temp = new Node();
\$current = new Node();

//2. if current node is not equal to head, delete the
//   current node and move current to next node using temp,
//   repeat the process till the current reaches the head
\$temp = \$current->next;
\$current = null;
\$current = \$temp;
}

}
echo "All nodes are deleted successfully.\n";
}
```

The below is a complete program that uses above discussed concept of deleting all nodes of a circular doubly linked list which makes the list empty with size zero.

```#include <iostream>
using namespace std;

//node structure
struct Node {
int data;
Node* next;
Node* prev;
};

private:
public:
}

//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;
} else {
temp = temp->next;
temp->next = newNode;
newNode->prev = temp;
}
}

//delete all nodes of the list
void deleteAllNodes() {
Node *temp, *current;
temp = current->next;
free(current);
current = temp;
}
}
cout<<"All nodes are deleted successfully.\n";
}

//display the content of the list
void PrintList() {
if(temp != NULL) {
cout<<"The list contains: ";
while(true) {
cout<<temp->data<<" ";
temp = temp->next;
break;
}
cout<<endl;
} else {
cout<<"The list is empty.\n";
}
}
};

// test the code
int main() {

//Add four elements in the list.
MyList.push_back(10);
MyList.push_back(20);
MyList.push_back(30);
MyList.push_back(40);

//Display the content of the list.
MyList.PrintList();

//delete all nodes of the list
MyList.deleteAllNodes();

//Display the content of the list.
MyList.PrintList();

return 0;
}
```

The above code will give the following output:

```The list contains: 10 20 30 40
All nodes are deleted successfully.
The list is empty.
```
```#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;
} else {
temp = temp->next;
}
temp->next = newNode;
newNode->prev = temp;
}
}

//delete all nodes of the list
struct Node *temp, *current;
temp = current->next;
free(current);
current = temp;
}
}
printf("All nodes are deleted successfully.\n");
}

//display the content of the list
printf("The list contains: ");
while (1) {
printf("%i ",temp->data);
temp = temp->next;
break;
}
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);

//Display the content of the list.
PrintList(MyList);

//delete all nodes of the list
deleteAllNodes(&MyList);

//Display the content of the list.
PrintList(MyList);

return 0;
}
```

The above code will give the following output:

```The list contains: 10 20 30 40
All nodes are deleted successfully.
The list is empty.
```
```# node structure
class Node:
def __init__(self, data):
self.data = data
self.next = None
self.prev = None

def __init__(self):

#Add new element at the end of the list
def push_back(self, newElement):
newNode = Node(newElement)
return
else:
temp = temp.next
temp.next = newNode
newNode.prev = temp

#delete all nodes of the list
def deleteAllNodes(self):
temp = current.next
current = None
current = temp
print("All nodes are deleted successfully.")

#display the content of the list
def PrintList(self):
if(temp != None):
print("The list contains:", end=" ")
while (True):
print(temp.data, end=" ")
temp = temp.next
break
print()
else:
print("The list is empty.")

# test the code

#Add four elements in the list.
MyList.push_back(10)
MyList.push_back(20)
MyList.push_back(30)
MyList.push_back(40)

#Display the content of the list.
MyList.PrintList()

#delete all nodes of the list
MyList.deleteAllNodes()

#Display the content of the list.
MyList.PrintList()
```

The above code will give the following output:

```The list contains: 10 20 30 40
All nodes are deleted successfully.
The list is empty.
```
```//node structure
class Node {
int data;
Node next;
Node prev;
};

}

//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;
} else {
Node temp = new Node();
temp = temp.next;
temp.next = newNode;
newNode.prev = temp;
}
}

//delete all nodes of the list
void deleteAllNodes() {
Node temp = new Node();
Node current = new Node();
temp = current.next;
current = null;
current = temp;
}
}
System.out.println("All nodes are deleted successfully.");
}

//display the content of the list
void PrintList() {
Node temp = new Node();
if(temp != null) {
System.out.print("The list contains: ");
while(true) {
System.out.print(temp.data + " ");
temp = temp.next;
break;
}
System.out.println();
} else {
System.out.println("The list is empty.");
}
}
};

// test the code
public class Implementation {
public static void main(String[] args) {

//Add four elements in the list.
MyList.push_back(10);
MyList.push_back(20);
MyList.push_back(30);
MyList.push_back(40);

//Display the content of the list.
MyList.PrintList();

//delete all nodes of the list
MyList.deleteAllNodes();

//Display the content of the list.
MyList.PrintList();
}
}
```

The above code will give the following output:

```The list contains: 10 20 30 40
All nodes are deleted successfully.
The list is empty.
```
```using System;

//node structure
class Node {
public int data;
public Node next;
public Node prev;
};

}

//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;
} else {
Node temp = new Node();
temp = temp.next;
temp.next = newNode;
newNode.prev = temp;
}
}

//delete all nodes of the list
public void deleteAllNodes() {
Node temp = new Node();
Node current = new Node();
temp = current.next;
current = null;
current = temp;
}
}
Console.WriteLine("All nodes are deleted successfully.");
}

//display the content of the list
public void PrintList() {
Node temp = new Node();
if(temp != null) {
Console.Write("The list contains: ");
while(true) {
Console.Write(temp.data + " ");
temp = temp.next;
break;
}
Console.WriteLine();
} else {
Console.WriteLine("The list is empty.");
}
}
};

// test the code
class Implementation {
static void Main(string[] args) {

//Add four elements in the list.
MyList.push_back(10);
MyList.push_back(20);
MyList.push_back(30);
MyList.push_back(40);

//Display the content of the list.
MyList.PrintList();

//delete all nodes of the list
MyList.deleteAllNodes();

//Display the content of the list.
MyList.PrintList();
}
}
```

The above code will give the following output:

```The list contains: 10 20 30 40
All nodes are deleted successfully.
The list is empty.
```
```<?php
//node structure
class Node {
public \$data;
public \$next;
public \$prev;
}

public function __construct(){
}

//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;
} else {
\$temp = new Node();
\$temp = \$temp->next;
}
\$temp->next = \$newNode;
\$newNode->prev = \$temp;
}
}

//delete all nodes of the list
public function deleteAllNodes() {
\$temp = new Node();
\$current = new Node();
\$temp = \$current->next;
\$current = null;
\$current = \$temp;
}
}
echo "All nodes are deleted successfully.\n";
}

//display the content of the list
public function PrintList() {
\$temp = new Node();
if(\$temp != null) {
echo "The list contains: ";
while(true) {
echo \$temp->data." ";
\$temp = \$temp->next;
break;
}
echo "\n";
} else {
echo "The list is empty.\n";
}
}
};

// test the code

//Add four elements in the list.
\$MyList->push_back(10);
\$MyList->push_back(20);
\$MyList->push_back(30);
\$MyList->push_back(40);

//Display the content of the list.
\$MyList->PrintList();

//delete all nodes of the list
\$MyList->deleteAllNodes();

//Display the content of the list.
\$MyList->PrintList();
?>
```

The above code will give the following output:

```The list contains: 10 20 30 40
All nodes are deleted successfully.
The list is empty.
```

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