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;
}

struct Node *insertAtFront(struct Node *head, int value) {
  struct Node *newNode = createNode(value);
  newNode->next = head;
  return newNode;
}

// Deletes the first node with this value, and returns the head
struct Node *deleteValue(struct Node *head, int value) {
  // The list is empty
  if (head == NULL) {
    return NULL;
  }

// Special case: delete the first node
  if (head->data == value) {
    struct Node *newHead = head->next;
    free(head);
    return newHead;
  }

// Find the node before the one to delete
  struct Node *current = head;
  while (current->next != NULL && current->next->data != value) {
    current = current->next;
  }

// Skip over the node, then free it
  if (current->next != NULL) {
    struct Node *toDelete = current->next;
    current->next = toDelete->next;
    free(toDelete);
  }

return 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;
  head = insertAtFront(head, 40);
  head = insertAtFront(head, 30);
  head = insertAtFront(head, 20);
  head = insertAtFront(head, 10);
  printList(head);

head = deleteValue(head, 20); // Delete from the middle
  printList(head);

head = deleteValue(head, 10); // Delete the first node
  printList(head);

freeList(head);
  return 0;
}