singly Linked List

Program to create and display singly Linked List.

C Program

#include<stdio.h>
#include<stdlib.h>
struct Node {
int data;
struct Node *next;
};
void display(struct Node *n)
{
while (n != NULL)
  {
printf(" %d \n", n->data);
     n = n->next;
  }
}
int main()
{
struct Node* head = NULL;
struct Node* second = NULL;
struct Node* third = NULL;
  // allocate 3 nodes in the heap  
head = (struct Node*)malloc(sizeof(struct Node)); 
second = (struct Node*)malloc(sizeof(struct Node));
third = (struct Node*)malloc(sizeof(struct Node));
head->data = 100; //assign data in first node
head->next = second; // Link first node with the second node
  // assign data to second node 
second->data = 200; 
  // Link second node with the third node
second->next = third;
third->data = 300; //assign data to third node
third->next = NULL;
display(head);
return 0;
}

Output:

100 
 200 
 300

Java Program

public class LinkedList
{
    Node head;  // head of list
static class Node {
int data;
        Node next;
Node(int d)  { data = d;  next=null; }
    }

    /* This function prints contents of the linked list starting from head */
public void display()
    {
        Node n = head;
while (n != null)
        {
System.out.print(n.data+" \n");
            n = n.next;
        }
    }

    /* method to create a simple linked list with 3 nodes*/
public static void main(String[] args)
    {
        /* Start with the empty list. */
LinkedList list = new LinkedList();

list.head       = new Node(100);
        Node second      = new Node(200);
        Node third       = new Node(300);

list.head.next = second; // Link first node with the second node
second.next = third; // Link first node with the second node

list.display();
    }
}

Output:

100 
 200 
 300

Python Program

# Node class
class Node:

    # Function to initialise the node object
    def __init__(self, data):
        self.data = data  # Assign data
        self.next = None  # Initialize next as null

# Linked List class contains a Node object
class LinkedList:

    # Function to initialize head
    def __init__(self):
        self.head = None

    # This function prints contents of linked list
    # starting from head
    def display(self):
        temp = self.head
        while (temp):
            print temp.data,
            temp = temp.next

# Code execution starts here
if __name__=='__main__':

    # Start with the empty list
    list = LinkedList()

    list.head  = Node(100)
    second = Node(200)
    third  = Node(300)

    list.head.next = second; # Link first node with second
    second.next = third; # Link second node with the third node

    list.display()

Output:

100 
 200 
 300

PHP Program

<?php
class Node
{
public $data;
public $next;

public function __construct($item)
    {
        $this->data = $item;
        $this->next = null;
    }
}

class LinkList
{
public $head = null;
public $second=null;
public $third=null;

private static $count = 0;
public function Insert() {
            $this->head = new Node(100);
           $this->second=new Node(200);
           $this->third=new Node(300);

            $this->head->next=$this->second;
            $this->second->next=$this->third;

        }


public function PrintAsList()
    {
        $items = [];
        $current = $this->head;
while($current != null) {
array_push($items, $current->data);
            $current = $current->next;
        }

        $str = '';
foreach($items as $item)
        {
            $str .= $item . ' ';
        }

echo $str;

echo PHP_EOL;
    }
}

$ll = new LinkList();

$ll->Insert();
$ll->PrintAsList();
echo PHP_EOL;
?>

Output:

100 
 200 
 300

Explanation

Linked List is a type of data structure in which information is stored in the form of a node which consists of data and address of next node. In a linked list, the node represents a single element.

Pictorial representation of a node:-

Representation of a node programmatically:-

struct Node
{
int data;
struct Node *next;
};

Java

class Node
    {  int data;
        Node next;          
        // Constructor to create a new node
        // Next is by default initialized as null
        Node(int d) {data = d;}
    }

Python

classNode:
  
    # Function to initialize the node object
    def__init__(self, data):
        self.data =data  # Assign data
        self.next=None  # Initialize 
                          # next as null

Php

class Node
{  public $data;
    public $next;
    public function __construct($item)    {
        $this->data = $item;
        $this->next = null;    }
}

By using the above syntax of creating a node in each language. A linked list is created by creating each node object and giving some value to the data section of the node and linking to the next node by using the next pointer.

Steps to create a linked list by using node:-

1. Firstly we will create an object of the node and initialize them. Each object represents the single node.

struct Node* head = NULL;
struct Node* second = NULL;
  head = (struct Node*)malloc(sizeof(struct Node)); 
  second = (struct Node*)malloc(sizeof(struct Node));
  third = (struct Node*)malloc(sizeof(struct Node));

Java

Node second      = new Node(200);
        Node third       = new Node(300);

Python

second = Node(200)
    third  = Node(300)

Php

public $head = null;
    public $second=null;
    public $third=null;
$this->head = new Node(100);
           $this->second=new Node(200);
           $this->third=new Node(300);

2. Finally, link nodes to each other. If there is no any next node to link, Next variable of node class will be initialized as null;

head->data = 100; //assign data in first node
  head->next = second; // Link first node with the second node

Java

list.head.next = second; // Link first node with the second node
second.next = third; // Link first node with the second node

Python

list.head.next = second; # Link first node with second
second.next = third; # Link second node with the third node

Php

$this->head->next=$this->second;
            $this->second->next=$this->third;

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Explanation

Steps to create a linked list by using node:-

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