# 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() {

//1. the list contains one node, delete
} else {

//2. if the list contains more than one node,
//   create two nodes - temp and firstNode, both

//3. using temp node, traverse to the last node
temp = temp->next;
}

free(firstNode);
}
}
}
```
```void pop_front(struct Node** head_ref) {

//1. the list contains one node, delete
} else {

//2. if the list contains more than one node,
//   create two nodes - temp and firstNode, both

//3. using temp node, traverse to the last node
temp = temp->next;
}

free(firstNode);
}
}
}
```
```def pop_front(self):

#1. the list contains one node, delete
else:

#2. if the list contains more than one node,
#   create two nodes - temp and firstNode, both

#3. using temp node, traverse to the last node
temp = temp.next

firstNode = None
```
```void pop_front() {

//1. the list contains one node, delete
} else {

//2. if the list contains more than one node,
//   create two nodes - temp and firstNode, both

//3. using temp node, traverse to the last node
temp = temp.next;
}

firstNode = null;
}
}
}
```
```public void pop_front() {

//1. the list contains one node, delete
} else {

//2. if the list contains more than one node,
//   create two nodes - temp and firstNode, both

//3. using temp node, traverse to the last node
temp = temp.next;
}

firstNode = null;
}
}
}
```
```public function pop_front() {

//1. the list contains one node, delete
} else {

//2. if the list contains more than one node,
//   create two nodes - temp and firstNode, both

//3. using temp node, traverse to the last node
\$temp = \$temp->next;
}

\$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;
};

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 first node of the list
void pop_front() {
} else {
temp = temp->next;
}
free(firstNode);
}
}
}

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

//Delete first node of the list
} else {
temp = temp->next;
}
free(firstNode);
}
}
}

//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 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

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 first node of the list
def pop_front(self):
else:
temp = temp.next
firstNode = None

#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 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;
};

}

//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 first node of the list
void pop_front() {
} else {
temp = temp.next;
}
firstNode = null;
}
}
}

//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 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;
};

}

//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 first node of the list
public void pop_front() {
} else {
temp = temp.next;
}
firstNode = null;
}
}
}

//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 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;
}

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 first node of the list
public function pop_front() {
} else {
\$temp = \$temp->next;
}
\$firstNode = null;
}
}
}

//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 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
```

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