Circular Singly Linked List - Delete the last node

In this method, the last node of the circular singly linked list is deleted. For example - if the given list is 10->20->30->40 and the last node is deleted, the list becomes 10->20->30.

Deleting the last node of the Circular Singly Linked List involves checking the head for empty. If it is not empty and contains only one node then delete the head node. If the list contains more than one node then traverse to the second last node of the list and link it with the head. Finally, delete the last node.

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

```void pop_back() {

} else {

//2. Else, traverse to the second last
//   element of the list
temp = temp->next;

//3. Change the next of the second
//   last node to head and delete the
//   last node
Node* lastNode = temp->next;
free(lastNode);
}
}
}
```
```void pop_back(struct Node** head_ref) {

} else {

//2. Else, traverse to the second last
//   element of the list
temp = temp->next;

//3. Change the next of the second
//   last node to head and delete the
//   last node
struct Node* lastNode = temp->next;
free(lastNode);
}
}
}
```
```def pop_back(self):

else:

#2. Else, traverse to the second last
#   element of the list
temp = temp.next

#3. Change the next of the second
#   last node to head and delete the
#   last node
lastNode = temp.next
lastNode = None
```
```void pop_back() {

} else {

//2. Else, traverse to the second last
//   element of the list
Node temp = new Node();
temp = temp.next;

//3. Change the next of the second
//   last node to head and delete the
//   last node
Node lastNode = temp.next;
lastNode = null;
}
}
}
```
```public void pop_back() {

} else {

//2. Else, traverse to the second last
//   element of the list
Node temp = new Node();
temp = temp.next;

//3. Change the next of the second
//   last node to head and delete the
//   last node
Node lastNode = temp.next;
lastNode = null;
}
}
}
```
```public function pop_back() {

} else {

//2. Else, traverse to the second last
//   element of the list
\$temp = new Node();
\$temp = \$temp->next;

//3. Change the next of the second
//   last node to head and delete the
//   last node
\$lastNode = \$temp->next;
\$lastNode = null;
}
}
}
```

The below is a complete program that uses above discussed concept of deleting the last node of the circular singly linked list.

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

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

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

//Delete last node of the list
void pop_back() {
} else {
temp = temp->next;
Node* lastNode = temp->next;
free(lastNode);
}
}
}

//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);
MyList.PrintList();

//Delete the last node
MyList.pop_back();
MyList.PrintList();

return 0;
}
```

The above code will give the following output:

```The list contains: 10 20 30 40
The list contains: 10 20 30
```
```#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** head_ref, int newElement) {
struct Node *newNode, *temp;
newNode = (struct Node*)malloc(sizeof(struct Node));
newNode->data = newElement;
newNode->next = NULL;
} else {
temp = temp->next;
}
temp->next = newNode;
}
}

//Delete last node of the list
} else {
temp = temp->next;
struct Node* lastNode = temp->next;
free(lastNode);
}
}
}

//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);
PrintList(MyList);

//Delete the last node
pop_back(&MyList);
PrintList(MyList);

return 0;
}
```

The above code will give the following output:

```The list contains: 10 20 30 40
The list contains: 10 20 30
```
```# node structure
class Node:
def __init__(self, data):
self.data = data
self.next = 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

#Delete last node of the list
def pop_back(self):
else:
temp = temp.next
lastNode = temp.next
lastNode = 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 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 last node
MyList.pop_back()
MyList.PrintList()
```

The above code will give the following output:

```The list contains: 10 20 30 40
The list contains: 10 20 30
```
```//node structure
class Node {
int data;
Node next;
};

}

//Add new element at the end of the list
void push_back(int newElement) {
Node newNode = new Node();
newNode.data = newElement;
newNode.next = null;
} else {
Node temp = new Node();
temp = temp.next;
temp.next = newNode;
}
}

//Delete last node of the list
void pop_back() {
} else {
Node temp = new Node();
temp = temp.next;
Node lastNode = temp.next;
lastNode = 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 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 last node
MyList.pop_back();
MyList.PrintList();
}
}
```

The above code will give the following output:

```The list contains: 10 20 30 40
The list contains: 10 20 30
```
```using System;

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

}

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

//Delete last node of the list
public void pop_back() {
} else {
Node temp = new Node();
temp = temp.next;
Node lastNode = temp.next;
lastNode = 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 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 last node
MyList.pop_back();
MyList.PrintList();
}
}
```

The above code will give the following output:

```The list contains: 10 20 30 40
The list contains: 10 20 30
```
```<?php
//node structure
class Node {
public \$data;
public \$next;
}

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

//Delete last node of the list
public function pop_back() {
} else {
\$temp = new Node();
\$temp = \$temp->next;
\$lastNode = \$temp->next;
\$lastNode = 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 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 last node
\$MyList->pop_back();
\$MyList->PrintList();
?>
```

The above code will give the following output:

```The list contains: 10 20 30 40
The list contains: 10 20 30
```

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