How to Create a Linked List in C?

A linked list is a data structure in which size can be modified dynamically during the runtime. In the linked list, each element is referred to as a node. Each node in the linked list stores data and a pointer to the next node present in the list. In this article, we will learn how to create a linked list in C.

Example

Input:
Elements for Linked list = {10,20,30,40,50}

Output:
Linked List: 10 -> 20 -> 30 -> 40 -> 50 -> NULL

Create a Linked List in C

Linked List in C can be created by defining a structure that represents the nodes i.e. having a data field and next pointer.

• We can then create the instances of this structure and join them using the next pointers.
• We will keep the pointer to the first element as the head of the linked list.
• We can traverse or refer to the linked list using the pointer to the head.

C Program Create a Linked List

C

// C Program to create a Linked List
#include <stdio.h>
#include <stdlib.h>

// Define the structure of Node
struct Node {
    int data;
    struct Node* next;
};

// Function to Insert Node in the Beginning
void insertAtBeginning(struct Node** head, int data)
{
    // create a new Node using dynamic memory allocation
    struct Node* newNode
        = (struct Node*)malloc(sizeof(struct Node));
    // store the data in the new Node
    newNode->data = data;
    // the next pointer of new Node will be on current head
    newNode->next = *head;
    // the current head will the new Node
    *head = newNode;
}

// Function to Insert the Node in the end
void insertAtEnd(struct Node** head, int data)
{
    struct Node* newNode
        = (struct Node*)malloc(sizeof(struct Node));
    // store the data in the new Node
    newNode->data = data;
    // Since the node will be last its next will be NULL
    newNode->next = NULL;
    // in case this is the first node make the newNode as
    // the head of the LinkedList
    if (*head == NULL) {
        *head = newNode;
        return;
    }
    // Create a pointer to iterate till the last node
    struct Node* current = *head;
    while (current->next != NULL) {
        current = current->next;
    }
    // make the next of the tail to the new Node
    current->next = newNode;
}

// Function to Print the Linked List
void printList(struct Node* head)
{
    struct Node* current = head;
    while (current != NULL) {
        printf("%d -> ", current->data);
        current = current->next;
    }
    printf("NULL\n");
}

int main()
{
    // Create the Linked List
    struct Node* head = NULL;
    // pass head by reference so that it can be modified
    insertAtBeginning(&head, 10);
    insertAtEnd(&head, 20);
    insertAtEnd(&head, 30);
    insertAtEnd(&head, 40);
    insertAtEnd(&head, 50);

    // Print the Linked List
    printf("Linked List: ");
    printList(head);

    return 0;
}

Output

Linked List: 10 -> 20 -> 30 -> 40 -> 50 -> NULL

Time Complexity: O(N) where N is the total number of nodes in the linked list.
Auxiliary Space: O(N)