Data Structures - Linked List Other Related Topics
Data Structures - Linked List Other Related Topics

Linked List - Delete all nodes

Deleting all nodes of a linked list requires traverse through the list and deleting each node one by one. It requires creating a temp node pointing to the head then move the head to head next. After that delete the temp node. Repeat the process till the head becomes null.

The function deleteAllNodes is created for this purpose. It is a 2-step process.

void deleteAllNodes() {
  
  //1. create a temp node
  Node* temp = new Node();
  
  //2. if the head is not null make temp as head and 
  //   move head to head next, then delete the temp,
  //   continue the process till head becomes null
  while(head != NULL) {
    temp = head;
    head = head->next;
    free(temp);
  }

  cout<<"All nodes are deleted successfully.\n";  
} 

void deleteAllNodes(struct Node** head_ref) {
  
  //1. create a temp node
  struct Node* temp;

  //2. if the head is not null make temp as head and 
  //   move head to head next, then delete the temp,
  //   continue the process till head becomes null
  while (*head_ref != NULL) {
    temp = *head_ref;
    *head_ref = (*head_ref)->next;
    free(temp);    
  }
  
  printf("All nodes are deleted successfully.\n");     
}

def deleteAllNodes(self):

  #1 & 2. create a temp node, if the head is not  
  #   null make temp as head and move head to head 
  #   next, then delete the temp, continue the 
  #   process till head becomes null
  while (self.head != None):
    temp = self.head
    self.head = self.head.next
    temp = None

  print("All nodes are deleted successfully.")    

void deleteAllNodes() {
  
  //1. create a temp node
  Node temp = new Node();
  
  //2. if the head is not null make temp as head and 
  //   move head to head next, then delete the temp,
  //   continue the process till head becomes null
  while(this.head != null) {
    temp = this.head;
    this.head = this.head.next;
    temp = null;
  }

  System.out.println("All nodes are deleted successfully.");
}    

public void deleteAllNodes() {
  
  //1. create a temp node
  Node temp = new Node();

  //2. if the head is not null make temp as head and 
  //   move head to head next, then delete the temp,
  //   continue the process till head becomes null
  while(this.head != null) {
    temp = this.head;
    this.head = this.head.next;
    temp = null;
  }

  Console.WriteLine("All nodes are deleted successfully."); 
}  

public function deleteAllNodes() {
  
  //1. create a temp node
  $temp = new Node();

  //2. if the head is not null make temp as head and 
  //   move head to head next, then delete the temp,
  //   continue the process till head becomes null
  while($this->head != null) {
    $temp = $this->head;
    $this->head = $this->head->next;
    $temp = null;
  }

  echo "All nodes are deleted successfully.\n"; 
}

The below is a complete program that uses above discussed concept of deleting all nodes of a linked list which makes the list empty with size zero.

#include <iostream>
using namespace std;

//node structure
struct Node {
    int data;
    Node* next;
};

class LinkedList {
  private:
    Node* head;
  public:
    LinkedList(){
      head = NULL;
    }
 
    //Add new element at the end of the list
    void push_back(int newElement) {
      Node* newNode = new Node();
      newNode->data = newElement;
      newNode->next = NULL; 
      if(head == NULL) {
        head = newNode;
      } else {
        Node* temp = head;
        while(temp->next != NULL)
          temp = temp->next;
        temp->next = newNode;
      }    
    }
    
    //delete all nodes of the list
    void deleteAllNodes() {
      Node* temp = new Node();
      while(head != NULL) {
        temp = head;
        head = head->next;
        free(temp);
      }
      cout<<"All nodes are deleted successfully.\n";  
    }

    //display the content of the list
    void PrintList() {
      Node* temp = head;
      if(temp != NULL) {
        cout<<"The list contains: ";
        while(temp != NULL) {
          cout<<temp->data<<" ";
          temp = temp->next;
        }
        cout<<"\n";
      } else {
        cout<<"The list is empty.\n";
      }
    }   
};

// test the code 
int main() {
  LinkedList MyList;

  //Add four elements in the list.
  MyList.push_back(10);
  MyList.push_back(20);
  MyList.push_back(30);
  MyList.push_back(40);

  //Display the content of the list.
  MyList.PrintList();

  //delete all nodes of the list
  MyList.deleteAllNodes();

  //Display the content of the list.
  MyList.PrintList();
  
  return 0; 
}

The above code will give the following output: 

The list contains: 10 20 30 40 
All nodes are deleted successfully.
The list is empty.

#include <stdio.h>
#include <stdlib.h>

//node structure
struct Node {
  int data;
  struct Node* next;
};

//Add new element at the end of the list
void push_back(struct Node** head_ref, int newElement) {  
  struct Node *newNode, *temp;
  newNode = (struct Node*)malloc(sizeof(struct Node)); 
  newNode->data = newElement;  
  newNode->next = NULL;
  if(*head_ref == NULL) {
    *head_ref = newNode; 
  } else {
    temp = *head_ref;
    while(temp->next != NULL) {
      temp = temp->next;
    }    
    temp->next = newNode;
  }
}

//delete all nodes of the list
void deleteAllNodes(struct Node** head_ref) {
  struct Node* temp;
  while (*head_ref != NULL) {
    temp = *head_ref;
    *head_ref = (*head_ref)->next;
    free(temp);    
  }  
  printf("All nodes are deleted successfully.\n");     
}

//display the content of the list
void PrintList(struct Node* head_ref) {
  struct Node* temp = head_ref;
  if(head_ref != NULL) {
    printf("The list contains: ");
    while (temp != NULL) {
      printf("%i ",temp->data);
      temp = temp->next;  
    }
    printf("\n");
  } else {
    printf("The list is empty.\n");
  }   
}

// test the code 
int main() {
  struct Node* MyList = NULL;

  //Add four elements in the list.
  push_back(&MyList, 10);
  push_back(&MyList, 20);
  push_back(&MyList, 30);
  push_back(&MyList, 40);

  //Display the content of the list.
  PrintList(MyList);

  //delete all nodes of the list
  deleteAllNodes(&MyList);

  //Display the content of the list.
  PrintList(MyList);

  return 0; 
}

The above code will give the following output: 

The list contains: 10 20 30 40 
All nodes are deleted successfully.
The list is empty.

# node structure
class Node:
  def __init__(self, data):
    self.data = data
    self.next = None

#class Linked List
class LinkedList:
  def __init__(self):
    self.head = None

  #Add new element at the end of the list
  def push_back(self, newElement):
    newNode = Node(newElement)
    if(self.head == None):
      self.head = newNode
      return
    else:
      temp = self.head
      while(temp.next != None):
        temp = temp.next
      temp.next = newNode

  #delete all nodes of the list
  def deleteAllNodes(self):
    while (self.head != None):
      temp = self.head
      self.head = self.head.next
      temp = None
    print("All nodes are deleted successfully.")  

  #display the content of the list
  def PrintList(self):
    temp = self.head
    if(temp != None):
      print("The list contains:", end=" ")
      while (temp != None):
        print(temp.data, end=" ")
        temp = temp.next
      print()
    else:
      print("The list is empty.")

# test the code                 
MyList = LinkedList()

#Add four elements in the list.
MyList.push_back(10)
MyList.push_back(20)
MyList.push_back(30)
MyList.push_back(40)

#Display the content of the list.
MyList.PrintList()

#delete all nodes of the list
MyList.deleteAllNodes()

#Display the content of the list.
MyList.PrintList()

The above code will give the following output: 

The list contains: 10 20 30 40 
All nodes are deleted successfully.
The list is empty.

//node structure
class Node {
    int data;
    Node next;
};

class LinkedList {
  Node head;

  LinkedList(){
    head = null;
  }

  //Add new element at the end of the list
  void push_back(int newElement) {
    Node newNode = new Node();
    newNode.data = newElement;
    newNode.next = null; 
    if(head == null) {
      head = newNode;
    } else {
      Node temp = new Node();
      temp = head;
      while(temp.next != null)
        temp = temp.next;
      temp.next = newNode;
    }    
  }

  //delete all nodes of the list
  void deleteAllNodes() {
    Node temp = new Node();
    while(this.head != null) {
      temp = this.head;
      this.head = this.head.next;
      temp = null;
    }
    System.out.println("All nodes are deleted successfully.");
  }    

  //display the content of the list
  void PrintList() {
    Node temp = new Node();
    temp = this.head;
    if(temp != null) {
      System.out.print("The list contains: ");
      while(temp != null) {
        System.out.print(temp.data + " ");
        temp = temp.next;
      }
      System.out.println();
    } else {
      System.out.println("The list is empty.");
    }
  }    
};

// test the code
public class Implementation {
  public static void main(String[] args) {
    LinkedList MyList = new LinkedList();

    //Add four elements in the list.
    MyList.push_back(10);
    MyList.push_back(20);
    MyList.push_back(30);
    MyList.push_back(40);

    //Display the content of the list.
    MyList.PrintList();

    //delete all nodes of the list
    MyList.deleteAllNodes();

    //Display the content of the list.
    MyList.PrintList();
  }
}

The above code will give the following output: 

The list contains: 10 20 30 40 
All nodes are deleted successfully.
The list is empty.

using System;

//node structure
class Node {
  public int data;
  public Node next;
};

class LinkedList {
  Node head;

  public LinkedList(){
    head = null;
  }
  
  //Add new element at the end of the list
  public void push_back(int newElement) {
    Node newNode = new Node();
    newNode.data = newElement;
    newNode.next = null; 
    if(head == null) {
      head = newNode;
    } else {
      Node temp = new Node();
      temp = head;
      while(temp.next != null)
        temp = temp.next;
      temp.next = newNode;
    }    
  }

  //delete all nodes of the list
  public void deleteAllNodes() {
    Node temp = new Node();
    while(this.head != null) {
      temp = this.head;
      this.head = this.head.next;
      temp = null;
    }
    Console.WriteLine("All nodes are deleted successfully."); 
  }    

  //display the content of the list
  public void PrintList() {
    Node temp = new Node();
    temp = this.head;
    if(temp != null) {
      Console.Write("The list contains: ");
      while(temp != null) {
        Console.Write(temp.data + " ");
        temp = temp.next;
      }
      Console.WriteLine();
    } else {
      Console.WriteLine("The list is empty.");
    }
  }     
};

// test the code
class Implementation {
  static void Main(string[] args) {
    LinkedList MyList = new LinkedList();

    //Add four elements in the list.
    MyList.push_back(10);
    MyList.push_back(20);
    MyList.push_back(30);
    MyList.push_back(40);

    //Display the content of the list.
    MyList.PrintList();  

    //delete all nodes of the list
    MyList.deleteAllNodes();

    //Display the content of the list.
    MyList.PrintList();
  }
}

The above code will give the following output: 

The list contains: 10 20 30 40 
All nodes are deleted successfully.
The list is empty.

<?php
//node structure
class Node {
  public $data;
  public $next;
}

class LinkedList {
  public $head;

  public function __construct(){
    $this->head = null;
  }
  
  //Add new element at the end of the list
  public function push_back($newElement) {
    $newNode = new Node();
    $newNode->data = $newElement;
    $newNode->next = null; 
    if($this->head == null) {
      $this->head = $newNode;
    } else {
      $temp = new Node();
      $temp = $this->head;
      while($temp->next != null) {
        $temp = $temp->next;
      }
      $temp->next = $newNode;
    }    
  }

  //delete all nodes of the list
  public function deleteAllNodes() {
    $temp = new Node();
    while($this->head != null) {
      $temp = $this->head;
      $this->head = $this->head->next;
      $temp = null;
    }
    echo "All nodes are deleted successfully.\n"; 
  }   

  //display the content of the list
  public function PrintList() {
    $temp = new Node();
    $temp = $this->head;
    if($temp != null) {
      echo "The list contains: ";
      while($temp != null) {
        echo $temp->data." ";
        $temp = $temp->next;
      }
      echo "\n";
    } else {
      echo "The list is empty.\n";
    }
  }   
};

// test the code 
$MyList = new LinkedList();

//Add four elements in the list.
$MyList->push_back(10);
$MyList->push_back(20);
$MyList->push_back(30);
$MyList->push_back(40);

//Display the content of the list.
$MyList->PrintList();

//delete all nodes of the list
$MyList->deleteAllNodes();

//Display the content of the list.
$MyList->PrintList();
?>

The above code will give the following output: 

The list contains: 10 20 30 40 
All nodes are deleted successfully.
The list is empty.
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