W3Schools Tryit Editor

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

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

struct Node *createNode(int value) {
  struct Node *newNode = malloc(sizeof(struct Node));
  if (newNode == NULL) {
    printf("Memory allocation failed\n");
    exit(1);
  }
  newNode->data = value;
  newNode->next = NULL;
  return newNode;
}

// Adds a node at the front, and returns the new head
struct Node *insertAtFront(struct Node *head, int value) {
  struct Node *newNode = createNode(value);
  newNode->next = head; // Step 1: point to the current head
  return newNode;       // Step 2: the new node is the new head
}

void printList(struct Node *head) {
  struct Node *current = head;
  while (current != NULL) {
    printf("%d -> ", current->data);
    current = current->next;
  }
  printf("NULL\n");
}

void freeList(struct Node *head) {
  while (head != NULL) {
    struct Node *next = head->next;
    free(head);
    head = next;
  }
}

int main() {
  struct Node *head = NULL; // An empty list

head = insertAtFront(head, 30);
  printList(head);

head = insertAtFront(head, 20);
  printList(head);

head = insertAtFront(head, 10);
  printList(head);

freeList(head);
  return 0;
}