# Program To Swap Nodes In A Singly Linked List Without Swapping Data

Program To Swap Nodes In A Singly Linked List Without Swapping Data on fibonacci, factorial, prime, armstrong, swap, reverse, search, sort, stack, queue, array, linkedlist, tree, graph etc.

## Program to swap nodes in a singly linked list without swapping data

### Explanation

In this program, we need to swap given two nodes in the singly linked list without swapping data.

One of the approaches to accomplish this task is to swap the previous nodes of the given two nodes and then, swap the next nodes of two nodes.

### Algorithm

1. Create a class Node which has two attributes: data and next. Next is a pointer to the next node in the list.
2. Create another class SwapNodes which has two attributes: head and tail.
1. Create a new node.
2. It first checks, whether the head is equal to null which means the list is empty.
3. If the list is empty, both head and tail will point to a newly added node.
4. If the list is not empty, the new node will be added to end of the list such that tail's next will point to a newly added node. This new node will become the new tail of the list.
4. swap() will swap the given two nodes present in the list:
1. Let n1 and n2 be the values need to be swapped.
2. If the list is empty then, return from the function.
3. If n1 and n2 are equal then, there will be no change in the list.
4. If the list is not empty then, search for n1 by traversing through the list such that prevNode1 which will point to node previous to node1 and node 1 will point to the node having value n1.
5. Similarly, search for n2 by traversing through the list such that prevNode2 which will point to node previous to node2 and node 2 will point to the node having value n2.
6. If prevNode1 points to head then, node2 will become head of the list. Similarly, if prevNode2 points to head then, node1 will become head of the list.
7. If prevNode1 or prevNode2 is not pointing to head then, swap the nodes such that prevNode1 will become the previous node of node2 and prevNode2 will become the previous node of node1.
8. Now, swap next nodes of node1 and node2.
5. display() will display the nodes present in the list:
1. Define a node current which will initially point to the head of the list.
2. Traverse through the list till current points to null.
3. Display each node by making current to point to node next to it in each iteration.

### Python

```#Represent a node of the singly linked list
class Node:
def __init__(self,data):
self.data = data;
self.next = None;

class SwapNodes:
def __init__(self):
self.tail = None;

#Create a new node
newNode = Node(data);

#Checks if the list is empty
#If list is empty, both head and tail will point to new node
self.tail = newNode;
else:
#newNode will be added after tail such that tail's next will point to newNode
self.tail.next = newNode;
#newNode will become new tail of the list
self.tail = newNode;

#swap() will swap the given two nodes
def swap(self, n1, n2):
prevNode1 = None;
prevNode2 = None;

#Checks if list is empty
return;

#If n1 and n2 are equal, then list will remain the same
if(n1 == n2):
return;

#Search for node1
while(node1 != None and node1.data != n1):
prevNode1 = node1;
node1 = node1.next;

#Search for node2
while(node2 != None and node2.data != n2):
prevNode2 = node2;
node2 = node2.next;

if(node1 != None and node2 != None):

#If previous node to node1 is not None then, it will point to node2
if(prevNode1 != None):
prevNode1.next = node2;
else:

#If previous node to node2 is not None then, it will point to node1
if(prevNode2 != None):
prevNode2.next = node1;
else:

#Swaps the next nodes of node1 and node2
temp = node1.next;
node1.next = node2.next;
node2.next = temp;
else:
print("Swapping is not possible");

#display() will display all the nodes present in the list
def display(self):
#Node current will point to head

print("List is empty");
return;
while(current != None):
#Prints each node by incrementing pointer
print(current.data),
current = current.next;

sList = SwapNodes();

print("Original list: ");
sList.display();

#Swaps the node 2 with node 5
sList.swap(2,5);

print("List after swapping nodes: ");
sList.display();
```

Output:

```Original list:
1 2 3 4 5
List after swapping nodes:
1 5 3 4 2
```

### C

```#include <stdio.h>

//Represent a node of the singly linked list
struct node{
int data;
struct node *next;
};

struct node *head, *tail = NULL;

//Create a new node
struct node *newNode = (struct node*)malloc(sizeof(struct node));
newNode->data = data;
newNode->next = NULL;

//Checks if the list is empty
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail->next = newNode;
//newNode will become new tail of the list
tail = newNode;
}
}

//swap() will swap the given two nodes
void swap(int n1, int n2){
struct node *prevNode1 = NULL, *prevNode2 = NULL, *node1 = head, *node2 = head, *temp = NULL;

//Checks if list is empty
return;
}

//If n1 and n2 are equal, then list will remain the same
if(n1 == n2)
return;

//Search for node1
while(node1 != NULL && node1->data != n1){
prevNode1 = node1;
node1 = node1->next;
}

//Search for node2
while(node2 != NULL && node2->data != n2){
prevNode2 = node2;
node2 = node2->next;
}

if(node1 != NULL && node2 != NULL) {

//If previous node to node1 is not null then, it will point to node2
if(prevNode1 != NULL)
prevNode1->next = node2;
else

//If previous node to node2 is not null then, it will point to node1
if(prevNode2 != NULL)
prevNode2->next = node1;
else

//Swaps the next nodes of node1 and node2
temp = node1->next;
node1->next = node2->next;
node2->next = temp;
}
else{
printf("Swapping is not possible\n");
}
}

//display() will display all the nodes present in the list
void display() {
//Node current will point to head

printf("List is empty\n");
return;
}
while(current != NULL) {
//Prints each node by incrementing pointer
printf("%d ", current->data);
current = current->next;
}
printf("\n");
}

int main()
{

printf("Original list: \n");
display();

//Swaps the node 2 with node 5
swap(2,5);

printf("List after swapping nodes: \n");
display();

return 0;
}
```

Output:

```Original list:
1 2 3 4 5
List after swapping nodes:
1 5 3 4 2
```

### JAVA

```public class SwapNodes {

//Represent a node of the singly linked list
class Node{
int data;
Node next;

public Node(int data) {
this.data = data;
this.next = null;
}
}

public Node tail = null;

//Create a new node
Node newNode = new Node(data);

//Checks if the list is empty
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail.next = newNode;
//newNode will become new tail of the list
tail = newNode;
}
}

//swap() will swap the given two nodes
public void swap(int n1, int n2){
Node prevNode1 = null, prevNode2 = null, node1 = head, node2 = head;

//Checks if list is empty
return;
}

//If n1 and n2 are equal, then list will remain the same
if(n1 == n2)
return;

//Search for node1
while(node1 != null && node1.data != n1){
prevNode1 = node1;
node1 = node1.next;
}

//Search for node2
while(node2 != null && node2.data != n2){
prevNode2 = node2;
node2 = node2.next;
}

if(node1 != null && node2 != null) {

//If previous node to node1 is not null then, it will point to node2
if(prevNode1 != null)
prevNode1.next = node2;
else

//If previous node to node2 is not null then, it will point to node1
if(prevNode2 != null)
prevNode2.next = node1;
else

//Swaps the next nodes of node1 and node2
Node temp = node1.next;
node1.next = node2.next;
node2.next = temp;
}
else {
System.out.println("Swapping is not possible");
}
}

//display() will display all the nodes present in the list
public void display() {
//Node current will point to head

System.out.println("List is empty");
return;
}
while(current != null) {
//Prints each node by incrementing pointer
System.out.print(current.data + " ");
current = current.next;
}
System.out.println();
}

public static void main(String[] args) {

SwapNodes sList = new SwapNodes();

System.out.println("Original list: ");
sList.display();

//Swaps the node 2 with node 5
sList.swap(2,5);

System.out.println("List after swapping nodes: ");
sList.display();
}
}
```

Output:

```Original list:
1 2 3 4 5
List after swapping nodes:
1 5 3 4 2
```

### C#

```using System;

public class CreateList
{
//Represent a node of the singly linked list
public class Node<T>{
public T data;
public Node<T> next;

public Node(T value) {
data = value;
next = null;
}
}

public class SwapNodes<T>{
public Node<T> tail = null;

//Create a new node
Node<T> newNode = new Node<T>(data);

//Checks if the list is empty
//If list is empty, both head and tail will point to new node
tail = newNode;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail.next = newNode;
//newNode will become new tail of the list
tail = newNode;
}
}

//swap() will swap the given two nodes
public void swap(int n1, int n2){
Node<T> prevNode1 = null, prevNode2 = null, node1 = head, node2 = head;

//Checks if list is empty
return;
}

//If n1 and n2 are equal, then list will remain the same
if(n1 == n2)
return;

//Search for node1
while(node1 != null && !(node1.data.Equals(n1))){
prevNode1 = node1;
node1 = node1.next;
}

//Search for node2
while(node2 != null && !(node2.data.Equals(n2))){
prevNode2 = node2;
node2 = node2.next;
}

if(node1 != null && node2 != null) {

//If previous node to node1 is not null then, it will point to node2
if(prevNode1 != null)
prevNode1.next = node2;
else

//If previous node to node2 is not null then, it will point to node1
if(prevNode2 != null)
prevNode2.next = node1;
else

//Swaps the next nodes of node1 and node2
Node<T> temp = node1.next;
node1.next = node2.next;
node2.next = temp;
}
else {
Console.WriteLine("Swapping is not possible");
}
}

//display() will display all the nodes present in the list
public void display() {
//Node current will point to head

Console.WriteLine("List is empty");
return;
}
while(current != null) {
//Prints each node by incrementing pointer
Console.Write(current.data + " ");
current = current.next;
}
Console.WriteLine();
}
}

public static void Main()
{
SwapNodes<int> sList = new SwapNodes<int>();

Console.WriteLine("Original list: ");
sList.display();

//Swaps the node 2 with node 5
sList.swap(2,5);

Console.WriteLine("List after swapping nodes: ");
sList.display();
}
}
```

Output:

```Original list:
1 2 3 4 5
List after swapping nodes:
1 5 3 4 2
```

### PHP

```<!DOCTYPE html>
<html>
<body>
<?php
//Represent a node of singly linked list
class Node{
public \$data;
public \$next;

function __construct(\$data){
\$this->data = \$data;
\$this->next = NULL;
}
}
class SwapNodes{
public \$tail;
function __construct(){
\$this->tail = NULL;
}

//Create a new node
\$newNode = new Node(\$data);

//Checks if the list is empty
//If list is empty, both head and tail will point to new node
\$this->tail = \$newNode;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
\$this->tail->next = \$newNode;
//newNode will become new tail of the list
\$this->tail = \$newNode;
}
}

//swap() will swap the given two nodes
function swap(\$n1, \$n2){
\$prevNode1 = null;
\$prevNode2 = null;

//Checks if list is empty
return;
}

//If n1 and n2 are equal, then list will remain the same
if(\$n1 == \$n2)
return;

//Search for node1
while(\$node1 != null && \$node1->data != \$n1){
\$prevNode1 = \$node1;
\$node1 = \$node1->next;
}

//Search for node2
while(\$node2 != null && \$node2->data != \$n2){
\$prevNode2 = \$node2;
\$node2 = \$node2->next;
}

if(\$node1 != null && \$node2 != null) {

//If previous node to node1 is not null then, it will point to node2
if(\$prevNode1 != null)
\$prevNode1->next = \$node2;
else

//If previous node to node2 is not null then, it will point to node1
if(\$prevNode2 != null)
\$prevNode2->next = \$node1;
else

//Swaps the next nodes of node1 and node2
\$temp = \$node1->next;
\$node1->next = \$node2->next;
\$node2->next = \$temp;
}
else {
print("Swapping is not possible <br>");
}
}

//display() will display all the nodes present in the list
function display() {
//Node current will point to head

print("List is empty <br>");
return;
}
while(\$current != NULL) {
//Prints each node by incrementing pointer
print(\$current->data . " ");
\$current = \$current->next;
}
print("<br>");
}
}

\$sList = new SwapNodes();

print("Original list: <br>");
\$sList->display();

//Swaps the node 2 with node 5
\$sList->swap(2,5);

print("List after swapping nodes: <br>");
\$sList->display();
?>
</body>
</html>
```

Output:

```Original list:
1 2 3 4 5
List after swapping nodes:
1 5 3 4 2
```

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