Program to Search an Element in a Doubly Linked List

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

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.
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.
addNode() will add node to the list:
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.
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:      #Represent the head and tail of the doubly linked list      def __init__(self):          self.head = None;          self.tail = None;                #addNode() will add a node to the list      def addNode(self, data):          #Create a new node          newNode = Node(data);                    #If list is empty          if(self.head == None):              #Both head and tail will point to newNode              self.head = self.tail = newNode;              #head’s previous will point to None              self.head.previous = 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          current = self.head;                    #Checks whether the list is empty          if(self.head == None):              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();  #Add nodes to the list  dList.addNode(1);  dList.addNode(5);  dList.addNode(4);  dList.addNode(2);  dList.addNode(3);     #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;  };         //Represent the head and tail of the doubly linked list  struct node *head, *tail = NULL;     //addNode() will add a node to the list  void addNode(int data) {      //Create a new node      struct node *newNode = (struct node*)malloc(sizeof(struct node));      newNode->data = data;            //If list is empty      if(head == NULL) {          //Both head and tail will point to newNode          head = tail = newNode;          //head’s previous will point to NULL          head->previous = 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      struct node *current = head;            //Checks whether the list is empty      if(head == NULL) {          printf(“List is emptyn”);          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 : %dn”, i);      else           printf(“Node is not present in the listn”);  }     int main()  {      //Add nodes to the list      addNode(1);      addNode(5);      addNode(4);      addNode(2);      addNode(3);            //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;          }      }            //Represent the head and tail of the doubly linked list      Node head, tail = null;            //addNode() will add a node to the list      public void addNode(int data) {          //Create a new node          Node newNode = new Node(data);                    //If list is empty          if(head == null) {              //Both head and tail will point to newNode              head = tail = newNode;              //head’s previous will point to null              head.previous = 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          Node current = head;                    //Checks whether the list is empty          if(head == null) {              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();          //Add nodes to the list          dList.addNode(1);          dList.addNode(5);          dList.addNode(4);          dList.addNode(2);          dList.addNode(3);                    //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;   namespace DoublyLinkedList   {                           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>{              //Represent the head and tail of the doubly linked list              protected Node<T> head = null;                            protected Node<T> tail = null;                            //addNode() will add a node to the list              public void addNode(T data) {                  //Create a new node                  Node<T> newNode = new Node<T>(data);                     //If list is empty                  if(head == null) {                      //Both head and tail will point to newNode                      head = tail = newNode;                      //head’s previous will point to null                      head.previous = 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                  Node<T> current = head;                     //Checks whether the list is empty                  if(head == null) {                      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>();              //Add nodes to the list              dList.addNode(1);              dList.addNode(5);              dList.addNode(4);              dList.addNode(2);              dList.addNode(3);                 //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{      //Represent the head and tail of the doubly linked list      public $head;      public $tail;      function __construct(){          $this->head = NULL;          $this->tail = NULL;      }            //addNode() will add a node to the list      function addNode($data){          //Create a new node          $newNode = new Node($data);                    //If list is empty          if($this->head == NULL) {              //Both head and tail will point to newNode              $this->head = $this->tail = $newNode;              //head’s previous will point to NULL              $this->head->previous = 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          $current = $this->head;                    //Checks whether the list is empty          if($this->head == NULL) {              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();  //Add nodes to the list  $dList->addNode(1);  $dList->addNode(5);  $dList->addNode(4);  $dList->addNode(2);  $dList->addNode(3);     //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

Next Topic#

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

Explanation

Algorithm

Solution

Python

C

JAVA

C#

PHP

Wind Energy

Basics of PyTorch

You may also like