Program to Delete a New Node From the Beginning of the Doubly Linked List

Q. Program to delete a new node from the beginning of the doubly linked list.

Explanation

In this program, we will create a doubly linked list and delete a node from the beginning of the list. If the list is empty, print the message “List is empty”. If the list is not empty, we will make the head to point to next node in the list then; we will delete the first node.

Consider the above example, new was the head of the list. Make head to point to next node in the list. Now, node 1 will become the new head of the list thus, deleting node new.

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.
deleteFromStart() will delete a node from the beginning of the list:
1. It first checks whether the head is null (empty list) then, it will return from the function as there is no node present in the list.
2. If the list is not empty, it will check whether the list has only one node.
3. If the list has only one node, it will set both head and tail to null.
4. If the list has more than one node then, the head will point to next node in the list and delete the old head node.
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 DeleteStart:      #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;                    #deleteFromStart() will delete a node from the beginning of the list      def deleteFromStart(self):          #Checks whether list is empty          if(self.head == None):              return;          else:              #Checks whether the list contains only one element              if(self.head != self.tail):                  #head will point to next node in the list                  self.head = self.head.next;                  #Previous node to current head will be made None                  self.head.previous = None;                                #If the list contains only one element               #then, it will remove the node, and now both head and tail will point to None                else:                  self.head = self.tail = None;                        #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;          while(current != None):              #Prints each node by incrementing pointer.              print(current.data),              current = current.next;          print();           dList = DeleteStart();  #Add nodes to the list  dList.addNode(1);  dList.addNode(2);  dList.addNode(3);  dList.addNode(4);  dList.addNode(5);     #Printing original list  print(“Original List: “);  dList.display();  while(dList.head != None):      dList.deleteFromStart();      #Printing updated list      print(“Updated List: “);      dList.display();  

Output:

Original List:   1 2 3 4 5   Updated List:   2 3 4 5   Updated List:   3 4 5   Updated List:   4 5   Updated List:   5   Updated List:   List is empty

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;      }  }     //deleteFromStart() will delete a node from the beginning of the list  void deleteFromStart() {      //Checks whether list is empty      if(head == NULL) {          return;      }      else {          //Checks whether the list contains only one element          if(head != tail) {              //head will point to next node in the list              head = head->next;              //Previous node to current head will be made NULL              head->previous = NULL;          }          //If the list contains only one element           //then, it will remove node and now both head and tail will point to NULL          else {              head = tail = NULL;          }      }  }     //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;      }      while(current != NULL) {          //Prints each node by incrementing pointer.          printf(“%d “,current->data);          current = current->next;      }      printf(“n”);  }        int main()  {      //Add nodes to the list      addNode(1);      addNode(2);      addNode(3);      addNode(4);      addNode(5);            //Printing original list      printf(“Original List: n”);      display();      while(head != NULL) {          deleteFromStart();          //Printing updated list          printf(“Updated List: n”);          display();      }             return 0;  }  

Output:

Original List:   1 2 3 4 5   Updated List:   2 3 4 5   Updated List:   3 4 5   Updated List:   4 5   Updated List:   5   Updated List:   List is empty

JAVA

  public class DeleteStart {            //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;          }      }            //deleteFromStart() will delete a node from the beginning of the list      public void deleteFromStart() {          //Checks whether list is empty          if(head == null) {              return;          }          else {              //Checks whether the list contains only one element              if(head != tail) {                  //head will point to next node in the list                  head = head.next;                  //Previous node to current head will be made null                  head.previous = null;              }              //If the list contains only one element               //then, it will remove node and now both head and tail will point to null              else {                  head = tail = null;              }          }      }            //display() will print out the nodes 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;          }          while(current != null) {              //Prints each node by incrementing the pointer.                System.out.print(current.data + ” “);              current = current.next;          }          System.out.println();      }            public static void main(String[] args) {                    DeleteStart dList = new DeleteStart();          //Add nodes to the list          dList.addNode(1);          dList.addNode(2);          dList.addNode(3);          dList.addNode(4);          dList.addNode(5);                    //Printing original list          System.out.println(“Original List: “);          dList.display();          while(dList.head != null) {              dList.deleteFromStart();              //Printing updated list              System.out.println(“Updated List: “);              dList.display();          }      }  }  

Output:

Original List:   1 2 3 4 5   Updated List:   2 3 4 5   Updated List:   3 4 5   Updated List:   4 5   Updated List:   5   Updated List:   List is empty

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 DeleteStart<T>{              //Represent the head and tail of the doubly linked list              public Node<T> head = null;                            public 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;                  }              }                    //deleteFromStart() will delete a node from the beginning of the list              public void deleteFromStart() {                  //Checks whether list is empty                  if(head == null) {                      return;                  }                  else {                      //Checks whether the list contains only one element                      if(head != tail) {                          //head will point to next node in the list                          head = head.next;                          //Previous node to current head will be made null                          head.previous = null;                      }                      //If the list contains only one element                       //then, it will remove node and now both head and tail will point to null                      else {                          head = tail = null;                      }                  }              }                    //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;                  }                  while(current != null) {                      //Prints each node by incrementing the pointer.                        Console.Write(current.data + ” “);                      current = current.next;                  }                  Console.WriteLine();              }          }                    public static void Main()          {              DeleteStart<int> dList = new DeleteStart<int>();              //Add nodes to the list              dList.addNode(1);              dList.addNode(2);              dList.addNode(3);              dList.addNode(4);              dList.addNode(5);                 //Printing original list              Console.WriteLine(“Original List: “);              dList.display();              while(dList.head != null) {                  dList.deleteFromStart();                  //Printing updated list                  Console.WriteLine(“Updated List: “);                  dList.display();              }          }          }  }  

Output:

Original List:   1 2 3 4 5   Updated List:   2 3 4 5   Updated List:   3 4 5   Updated List:   4 5   Updated List:   5   Updated List:   List is empty

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 DeleteStart{      //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              $this->tail->next = NULL;          }      }            //deleteFromStart() will delete a node from the beginning of the list      function deleteFromStart() {          //Checks whether list is empty          if($this->head == NULL) {              return;          }          else {              //Checks whether the list contains only one element              if($this->head != $this->tail) {                  //head will point to next node in the list                  $this->head = $this->head->next;                  //Previous node to current head will be made NULL                  $this->head->previous = NULL;              }              //If the list contains only one element               //then, it will remove node and now both head and tail will point to NULL              else {                  $this->head = $this->tail = NULL;              }          }      }            //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;          }          while($current != NULL) {              //Prints each node by incrementing pointer.              print($current->data . ” “);              $current = $current->next;          }          print(“<br>”);      }  }        $dList = new DeleteStart();  //Add nodes to the list  $dList->addNode(1);  $dList->addNode(2);  $dList->addNode(3);  $dList->addNode(4);  $dList->addNode(5);     //Printing original list  print(“Original List: <br>”);  $dList->display();  while($dList->head != NULL) {      $dList->deleteFromStart();      //Printing updated list      print(“Updated List: <br>”);      $dList->display();  }  ?>  </body>  </html>  

Output:

Original List:   1 2 3 4 5   Updated List:   2 3 4 5   Updated List:   3 4 5   Updated List:   4 5   Updated List:   5   Updated List:   List is empty

Next Topic#

Q. Program to delete a new node from the beginning of the doubly linked list.

Explanation

Algorithm

Solution

Python

C

JAVA

C#

PHP

Potential Energy

Program to Find The Transpose of a Given Matrix

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