How to Create a Linked List in C: Syntax and Example

To create a linked list in C, define a struct for the node containing data and a pointer to the next node. Then, dynamically allocate nodes using malloc and link them by setting the next pointers.

Syntax

A linked list node in C is defined using a struct that contains two parts:

• Data: The value stored in the node (e.g., an integer).
• Next pointer: A pointer to the next node in the list.

Example syntax:

c

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

Example

This example creates a linked list with three nodes holding values 10, 20, and 30, then prints them.

c

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

struct Node {
    int data;
    struct Node* 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));

    // Assign data and link nodes
    head->data = 10;
    head->next = second;

    second->data = 20;
    second->next = third;

    third->data = 30;
    third->next = NULL;

    // Print the linked list
    struct Node* current = head;
    while (current != NULL) {
        printf("%d ", current->data);
        current = current->next;
    }
    printf("\n");

    // Free allocated memory
    free(third);
    free(second);
    free(head);

    return 0;
}

Output

10 20 30 

Common Pitfalls

• Forgetting to allocate memory with malloc causes undefined behavior.
• Not setting the next pointer to NULL at the end leads to errors when traversing.
• Failing to free allocated memory causes memory leaks.
• Mixing up struct Node* and Node types can cause compilation errors.

c

/* Wrong: Missing malloc and next pointer */
struct Node node1;
node1.data = 5;
// node1.next is uninitialized

/* Right: Using malloc and setting next to NULL */
struct Node* node1 = (struct Node*)malloc(sizeof(struct Node));
node1->data = 5;
node1->next = NULL;

Quick Reference

• Define node with struct containing data and next pointer.
• Use malloc to create nodes dynamically.
• Link nodes by setting next pointers.
• Traverse list by following next until NULL.
• Always free memory with free when done.

Key Takeaways

A linked list node in C is a struct with data and a pointer to the next node.

Use malloc to allocate memory for each node and link them with next pointers.

Always set the last node's next pointer to NULL to mark the list end.

Traverse the list by moving from one node to the next until NULL is reached.

Free all allocated memory to avoid memory leaks.