Linked list : A Linked list is a data structure which is collection of zero or more nodes where each node has some information. The pictorial representation of the node is shown below.
A linked list is a linear data structure that includes a series of connected nodes. Here, each node store the data and the address of the next node. For example,
You have to start somewhere, so we give the address of the first node a special name called HEAD. Also, the last node in the linked list can be identified because its next portion points to NULL.
Linked list Representation :
Let's see how each node of the linked list is represented. Each node consists:
- A data item
- An address of another node
We wrap both the data item and the next node reference in a struct
struct node { int data; struct node *next; };
Understanding the structure of a linked list node is the key to having a grasp on it.
Each struct node has a data item and a pointer to another struct node. Let us create a simple Linked List with three items to understand how this works.
/* Initialize nodes */ struct node *head; struct node *one = NULL; struct node *two = NULL; struct node *three = NULL; /* Allocate memory */ one = malloc(sizeof(struct node)); two = malloc(sizeof(struct node)); three = malloc(sizeof(struct node)); /* Assign data values */ one->data = 1; two->data = 2; three->data=3; /* Connect nodes */ one->next = two; two->next = three; three->next = NULL; /* Save address of first node in head */ head = one;
If you didn't understand any of the lines above, all you need is a refresher on pointers and structs.
In just a few steps, we have created a simple linked list with three nodes.
The power of a linked list comes from the ability to break the chain and rejoin it. E.g. if you wanted to put an element 4 between 1 and 2, the steps would be:
- Create a new struct node and allocate memory to it.
- Add its data value as 4
- Point its next pointer to the struct node containing 2 as the data value
- Change the next pointer of "1" to the node we just created.
Doing something similar in an array would have required shifting the positions of all the subsequent elements.
In python and Java, the linked list can be implemented using classes as shown in the codes below.
Linked List Utility
Lists are one of the most popular and efficient data structures, with implementation in every programming language like C, C++, Python, Java, and C#.
Apart from that, linked lists are a great way to learn how pointers work. By practicing how to manipulate linked lists, you can prepare yourself to learn more advanced data structures like graphs and trees.
Linked List Implementations in C and Java:
Implementations in C:
// Linked list implementation in C
#include <stdio.h>
#include <stdlib.h>
// Creating a node
struct node {
int value;
struct node *next;
};
// print the linked list value
void printLinkedlist(struct node *p) {
while (p != NULL) {
printf("%d ", p->value);
p = p->next;
}
}
int main() {
// Initialize nodes
struct node *head;
struct node *one = NULL;
struct node *two = NULL;
struct node *three = NULL;
// Allocate memory
one = malloc(sizeof(struct node));
two = malloc(sizeof(struct node));
three = malloc(sizeof(struct node));
// Assign value values
one->value = 1;
two->value = 2;
three->value = 3;
// Connect nodes
one->next = two;
two->next = three;
three->next = NULL;
// printing node-value
head = one;
printLinkedlist(head);
}
Implementations in java:
// Linked list implementation in Java
class LinkedList {
// Creating a node
Node head;
static class Node {
int value;
Node next;
Node(int d) {
value = d;
next = null;
}
}
public static void main(String[] args) {
LinkedList linkedList = new LinkedList();
// Assign value values
linkedList.head = new Node(1);
Node second = new Node(2);
Node third = new Node(3);
// Connect nodess
linkedList.head.next = second;
second.next = third;
// printing node-value
while (linkedList.head != null) {
System.out.print(linkedList.head.value + " ");
linkedList.head = linkedList.head.next;
}
}
}
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