# Program to Search an Element in a Doubly Linked List

Program to Search an Element in a Doubly Linked List on fibonacci, factorial, prime, armstrong, swap, reverse, search, sort, stack, queue, array, linkedlist, tree, graph etc.

## Q. Program to search an element in a doubly linked list

### Explanation

In this program, we need to search a given node in a doubly linked list.

To solve this problem, we will traverse through the list using a node current. Current points to head and start comparing searched node data with current node data. If they are equal, set the flag to true and print the message along with the position of the searched node.

For, eg. In above list, a search node says 4 can be found at the position 3.

### Algorithm

1. Define a Node class which represents a node in the list. It will have three properties: data, previous which will point to the previous node and next which will point to the next node.
2. Define another class for creating a doubly linked list, and it has two nodes: head and tail. Initially, head and tail will point to null.
1. It first checks whether the head is null, then it will insert the node as the head.
2. Both head and tail will point to a newly added node.
3. Head's previous pointer will point to null and tail's next pointer will point to null.
4. If the head is not null, the new node will be inserted at the end of the list such that new node's previous pointer will point to tail.
5. The new node will become the new tail. Tail's next pointer will point to null.
4. searchNode() will search for a node in the list:
1. Variable i will keep track of the position of the searched node.
2. The variable flag will store boolean value false.
3. Current will point to head node.
4. Iterate through the loop by incrementing current to current.next and i to i + 1.
5. Compare each node's data with the searched node. If a match is found, set flag to true.
6. If the flag is true, prints the position of the searched node.
7. Else, print the message "Element is not present in the list".

## Solution

### Python

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

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

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

#If list is empty
#Both head and tail will point to newNode
#head's previous will point to None
#tail's next will point to None, as it is the last node of the list
self.tail.next = None;
else:
#newNode will be added after tail such that tail's next will point to newNode
self.tail.next = newNode;
#newNode's previous will point to tail
newNode.previous = self.tail;
#newNode will become new tail
self.tail = newNode;
#As it is last node, tail's next will point to None
self.tail.next = None;

#searchNode() will search a given node in the list
def searchNode(self, value):
i = 1;
flag = False;
#Node current will point to head

#Checks whether the list is empty
print("List is empty");
return;

while(current != None):
#Compare value to be searched with each node in the list
if(current.data == value):
flag = True;
break;
current = current.next;
i = i + 1;

if(flag):
print("Node is present in the list at the position : " + str(i));
else:
print("Node is not present in the list");

dList = SearchList();

#Search for node 4 in the list
dList.searchNode(4);

#Search for node 9 in the list
dList.searchNode(9);
```

Output:

```Node is present in the list at the position : 3
Node is not present in the list
```

### C

```#include <stdio.h>
#include <stdbool.h>

//Represent a node of the doubly linked list

struct node{
int data;
struct node *previous;
struct node *next;
};

struct node *head, *tail = NULL;

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

//If list is empty
//Both head and tail will point to newNode
//head's previous will point to NULL
//tail's next will point to NULL, as it is the last node of the list
tail->next = NULL;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail->next = newNode;
//newNode's previous will point to tail
newNode->previous = tail;
//newNode will become new tail
tail = newNode;
//As it is last node, tail's next will point to NULL
tail->next = NULL;
}
}

//searchNode() will search a given node in the list
void searchNode(int value) {
int i = 1;
bool flag = false;
//Node current will point to head

//Checks whether the list is empty
printf("List is empty\n");
return;
}
while(current != NULL) {
//Compare value to be searched with each node in the list
if(current->data == value) {
flag = true;
break;
}
current = current->next;
i++;
}
if(flag)
printf("Node is present in the list at the position : %d\n", i);
else
printf("Node is not present in the list\n");
}

int main()
{

//Search for node 4 in the list
searchNode(4);
//Search for node 9 in the list
searchNode(9);

return 0;
}
```

Output:

```Node is present in the list at the position : 3
Node is not present in the list
```

### JAVA

```public class SearchList {

//Represent a node of the doubly linked list

class Node{
int data;
Node previous;
Node next;

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

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

//If list is empty
//Both head and tail will point to newNode
//head's previous will point to null
//tail's next will point to null, as it is the last node of the list
tail.next = null;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail.next = newNode;
//newNode's previous will point to tail
newNode.previous = tail;
//newNode will become new tail
tail = newNode;
//As it is last node, tail's next will point to null
tail.next = null;
}
}

//searchNode() will search a given node in the list
public void searchNode(int value) {
int i = 1;
boolean flag = false;
//Node current will point to head

//Checks whether the list is empty
System.out.println("List is empty");
return;
}
while(current != null) {
//Compare value to be searched with each node in the list
if(current.data == value) {
flag = true;
break;
}
current = current.next;
i++;
}
if(flag)
System.out.println("Node is present in the list at the position : " + i);
else
System.out.println("Node is not present in the list");
}

public static void main(String[] args) {

SearchList dList = new SearchList();

//Search for node 4 in the list
dList.searchNode(4);
//Search for node 9 in the list
dList.searchNode(9);
}
}
```

Output:

```Node is present in the list at the position : 3
Node is not present in the list
```

### C#

```using System;
{
public class Program
{
//Represent a node of the doubly linked list

public class Node<T>{
public T data;
public Node<T> previous;
public Node<T> next;

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

public class SearchList<T>{
protected Node<T> tail = null;

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

//If list is empty
//Both head and tail will point to newNode
//head's previous will point to null
//tail's next will point to null, as it is the last node of the list
tail.next = null;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
tail.next = newNode;
//newNode's previous will point to tail
newNode.previous = tail;
//newNode will become new tail
tail = newNode;
//As it is last node, tail's next will point to null
tail.next = null;
}
}

//searchNode() will search a given node in the list
public void searchNode(int value) {
int i = 1;
bool flag = false;
//Node current will point to head

//Checks whether the list is empty
Console.WriteLine("List is empty");
return;
}
while(current != null) {
//Compare value to be searched with each node in the list
if(current.data.Equals(value)) {
flag = true;
break;
}
current = current.next;
i++;
}
if(flag)
Console.WriteLine("Node is present in the list at the position : " + i);
else
Console.WriteLine("Node is not present in the list");
}
}

public static void Main()
{
SearchList<int> dList = new SearchList<int>();

//Search for node 4 in the list
dList.searchNode(4);
//Search for node 9 in the list
dList.searchNode(9);
}
}
}
```

Output:

```Node is present in the list at the position : 3
Node is not present in the list
```

### PHP

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

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

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

//If list is empty
//Both head and tail will point to newNode
//head's previous will point to NULL
//tail's next will point to NULL, as it is the last node of the list
\$this->tail->next = NULL;
}
else {
//newNode will be added after tail such that tail's next will point to newNode
\$this->tail->next = \$newNode;
//newNode's previous will point to tail
\$newNode->previous = \$this->tail;
//newNode will become new tail
\$this->tail = \$newNode;
//As it is last node, tail's next will point to NULL
\$this->tail->next = NULL;
}
}

//searchNode() will search a given node in the list
function searchNode(\$value) {
\$i = 1;
\$flag = false;
//Node current will point to head

//Checks whether the list is empty
print("List is empty");
return;
}
while(\$current != NULL) {
//Compare value to be searched with each node in the list
if(\$current->data == \$value) {
\$flag = true;
break;
}
\$current = \$current->next;
\$i++;
}
if(\$flag)
print("Node is present in the list at the position : " . \$i);
else
print("Node is not present in the list");
}
}

\$dList = new SearchList();

//Search for node 4 in the list
\$dList->searchNode(4);
print("<br>");
//Search for node 9 in the list
\$dList->searchNode(9);
?>
</body>
</html>
```

Output:

```Node is present in the list at the position : 3
Node is not present in the list
```

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