Linked List

linked_list.c

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

struct node {
	int key;
	int data;
	struct node *next;
};

struct node *head = NULL;

void insert_first (int key, int data)
{
	/* allocate memory for this node */
	struct node *link = (struct node *) malloc (sizeof(struct node));
	link->key = key;
	link->data = data;
	/* point it to old first node */
	link->next = head;
	/* point first to new first node */
	head = link;
}

void print_list()
{
	struct node *current = head;
	while (current != NULL) {
		printf ("[%d,%d]\n", current->key, current->data);
		current = current->next;
	}
}
void delete_first()
{
  struct node *tmp = head->next;
  free (head);
  head = tmp;
}

void reverse()
{
  struct node *new_head = NULL;
  struct node *current = head;
  struct node *temp;
  while (current != NULL) {
    struct node *link = (struct node *) malloc (sizeof(struct node));
    link->key = current->key;
    link->data = current->data;
    link->next = current->next;
    new_head = link;
		temp = current;
    current = current->next;
    free (temp);
  }
  head = new_head;
}
    
int main(void)
{
	printf ("is empty linked list? %s\n", is_empty() ? "YES" : "NO");

	insert_first (1, 38);
	insert_first (2, -15);
	insert_first (3, 87);
	
	print_list();

	while (!is_empty()) {
		struct node *temp = delete_first();
		printf ("Deleted value:");
		printf ("[%d, %d]\n", temp->key, temp->data);
		free (temp);
	}

	insert_first (1, 38);
	insert_first (2, -15);
	insert_first (3, 87);

	print_list();
	
	printf ("reverse linked list:\n");
	reverse();
	
	print_list();

	return 0;
}