Program to Create a Doubly Linked List of N Nodes and Count the Number of Nodes

Q. Program to create a doubly linked list of n nodes and count the number of nodes.

Explanation

In this program, we will create a doubly linked list and count the number of nodes present in the list. To count the node, we traverse through the list by incrementing the counter by 1.

Program to create a doubly linked list of n nodes and count the number of nodes

What count of nodes presents above doubly linked list is 5.

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.
countNodes() will count the number of nodes present in the list.
1. Define a variable counter and new node current which will point to the head node.
2. Traverse through the list to count the nodes by making the current node to point to next node in the list till current point to null.
3. Increment the counter by 1.
display() will show all the nodes present in the list.
1. Define a new node ‘current’ that will point to the head.
2. Print current.data till current points to null.
3. Current will point to the next node in the list in each iteration.

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 CountList:      #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;                    #countNodes() will count the nodes present in the list      def countNodes(self):          counter = 0;          #Node current will point to head          current = self.head;                    while(current != None):              #Increment the counter by 1 for each node              counter = counter + 1;              current = current.next;          return counter;                    #display() will print out the nodes of the list      def display(self):          #Node current will point to head          current = self.head;          if(self.head == None):              print(“List is empty”);              return;          print(“Nodes of doubly linked list: “);          while(current != None):               #Prints each node by incrementing pointer.              print(current.data),              current = current.next;                dList = CountList();  #Add nodes to the list  dList.addNode(1);  dList.addNode(2);  dList.addNode(3);  dList.addNode(4);  dList.addNode(5);     #Displays the nodes present in the list  dList.display();     #Counts the nodes present in the given list  print(“nCount of nodes present in the list: ” + str(dList.countNodes()));  

Output:

Nodes of doubly linked list:   1 2 3 4 5   Count of nodes present in the list: 5

C

  #include <stdio.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;      }  }     //countNodes() will count the nodes present in the list  int countNodes() {      int counter = 0;      //Node current will point to head      struct node *current = head;            while(current != NULL) {          //Increment the counter by 1 for each node          counter++;          current = current->next;      }      return counter;  }        //display() will print out the nodes of the list  void display() {      //Node current will point to head      struct node *current = head;      if(head == NULL) {          printf(“List is emptyn”);          return;      }      printf(“Nodes of doubly linked list: n”);      while(current != NULL) {          //Prints each node by incrementing pointer.          printf(“%d “, current->data);          current = current->next;      }  }     int main()  {      //Add nodes to the list      addNode(1);      addNode(2);      addNode(3);      addNode(4);      addNode(5);            //Displays the nodes present in the list      display();            //Counts the nodes present in the given list      printf(“nCount of nodes present in the list: %d”, countNodes());         return 0;  }  

Output:

Nodes of doubly linked list:   1 2 3 4 5   Count of nodes present in the list: 5

JAVA

  public class CountList {            //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;          }      }            //countNodes() will count the nodes present in the list      public int countNodes() {          int counter = 0;          //Node current will point to head          Node current = head;                    while(current != null) {              //Increment the counter by 1 for each node              counter++;              current = current.next;          }          return counter;      }            //display() will print out the elements of the list      public void display() {          //Node current will point to head          Node current = head;          if(head == null) {              System.out.println(“List is empty”);              return;          }          System.out.println(“Nodes of doubly linked list: “);          while(current != null) {              //Prints each node by incrementing the pointer.                System.out.print(current.data + ” “);              current = current.next;          }      }            public static void main(String[] args) {                    CountList dList = new CountList();          //Add nodes to the list          dList.addNode(1);          dList.addNode(2);          dList.addNode(3);          dList.addNode(4);          dList.addNode(5);                    //Displays the nodes present in the list          dList.display();                    //Counts the nodes present in the given list          System.out.println(“nCount of nodes present in the list: ” + dList.countNodes());      }  }  

Output:

Nodes of doubly linked list:   1 2 3 4 5   Count of nodes present in the list: 5

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 CountList<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;                  }              }                            //countNodes() will count the nodes present in the list              public int countNodes() {                  int counter = 0;                  //Node current will point to head                  Node<T> current = head;                     while(current != null) {                      //Increment the counter by 1 for each node                      counter++;                      current = current.next;                  }                  return counter;              }                            //display() will print out the nodes of the list              public void display() {                  //Node current will point to head                  Node<T> current = head;                  if(head == null) {                      Console.WriteLine(“List is empty”);                      return;                  }                  Console.WriteLine(“Nodes of doubly linked list: “);                  while(current != null) {                      //Prints each node by incrementing the pointer.                        Console.Write(current.data + ” “);                      current = current.next;                  }              }          }                    public static void Main()          {              CountList<int> dList = new CountList<int>();              //Add nodes to the list              dList.addNode(1);              dList.addNode(2);              dList.addNode(3);              dList.addNode(4);              dList.addNode(5);                 //Displays the nodes present in the list              dList.display();                 //Counts the nodes present in the given list              Console.WriteLine(“nCount of nodes present in the list: ” + dList.countNodes());          }          }  }  

Output:

Nodes of doubly linked list:   1 2 3 4 5   Count of nodes present in the list: 5

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 CountList{      //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;          }      }            //countNodes() will count the nodes present in the list      function countNodes() {          $counter = 0;          //Node current will point to head          $current = $this->head;                    while($current != NULL) {              //Increment the counter by 1 for each node              $counter++;              $current = $current->next;          }          return $counter;      }            //display() will print out the nodes of the list      function display() {          //Node current will point to head          $current = $this->head;          if($this->head == NULL) {              print(“List is empty <br>”);              return;          }          print(“Nodes of doubly linked list: <br>”);          while($current != NULL) {              //Prints each node by incrementing pointer.              print($current->data . ” “);              $current = $current->next;          }      }  }        $dList = new CountList();  //Add nodes to the list  $dList->addNode(1);  $dList->addNode(2);  $dList->addNode(3);  $dList->addNode(4);  $dList->addNode(5);     //Displays the nodes present in the list  $dList->display();     //Counts the nodes present in the given list  print(“<br>Count of nodes present in the list: ” . $dList->countNodes());  ?>  </body>  </html>  

Output:

Nodes of doubly linked list:   1 2 3 4 5   Count of nodes present in the list: 5

Next Topic#

Q. Program to create a doubly linked list of n nodes and count the number of nodes.

Explanation

Algorithm

Solution

Python

C

JAVA

C#

PHP

Potential Energy

Program to Find The Transpose of a Given Matrix

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