Linked List in C

clink1.c

/*
 * Mon Jul 02 2012 - Weinan Li <[email protected]> - 0.1
 * - Initial version
 */

/* 
 * include printf()
 * and definitions of NULL
 */
#include <stdio.h>

/*
 * for malloc() and free()
 */
#include <stdlib.h>

struct node {
	int val;
	struct node *next, *prev;
};

struct list {
	struct node *head;
	struct node *curr;
	int size;
};

struct list* init_list(int head_val);
struct node* init_node(int val);
struct node* insert_node(struct list *the_list, int val);
void delete_node(struct list *the_list, struct node *node_to_delete);


struct list* init_list(int head_val) {
	struct list *new_list;
	new_list = malloc(sizeof(struct list));
	if (new_list == NULL) {
		return NULL;
	}
	
	struct node *head_node;
	head_node = init_node(head_val);
	if (head_node == NULL) {
		free(new_list);
		return NULL;
	}
	
	new_list->head = head_node;
	new_list->curr = head_node;
	new_list->size = 1;
	return new_list;
}

struct node* init_node(int val) {
	struct node *the_node;
	
	the_node = malloc(sizeof(struct node));
	
	if (the_node == NULL) {
		return NULL;
	}
	
	the_node->val = val;
	the_node->next = NULL;
	the_node->prev = NULL;	
	
	return the_node;
}

struct node* insert_node(struct list *the_list, int val) {
	struct node *new_node;
	new_node = init_node(val);
	
	if (new_node == NULL) {
		return NULL;
	}
	
	the_list->curr->next = new_node;
	new_node->prev = the_list->curr;
	the_list->curr = new_node;
	the_list->size++;
	
	return new_node;
}

void delete_node(struct list *the_list, struct node *node_to_delete) {
	if (the_list == NULL || node_to_delete == NULL)
		return;
	
	struct node* p = the_list->head;
	
	while(p!=NULL) {
		if (p == node_to_delete) {
			if (p == the_list->head) {
				the_list->head = the_list->head->next;
			} else {
				p->prev->next = p->next;
			}
			
			the_list->size--;
			
			free(p);
			return;
		}
		
		p = p->next;
	}
	
}


int main() {
	struct list *my_list = init_list(1);
	printf("Head of my list: %d\n", my_list->head->val);
	printf("Size of my list: %d\n", my_list->size);
	
	insert_node(my_list, 2);
	printf("Current node value: %d\n", my_list->curr->val);
	printf("Size of my list: %d\n", my_list->size);
	
	insert_node(my_list, 3);
	struct node *p = insert_node(my_list, 4);
	insert_node(my_list, 5);
	
	struct node *iter = my_list->head;
	while(iter != NULL) {
		printf("%d\t", iter->val);
		iter = iter->next;
	}
	

	delete_node(my_list, p);
	iter = my_list->head;
	printf("\nAfter delete:\n");
	while(iter != NULL) {
		printf("%d\t", iter->val);
		iter = iter->next;
	}
	printf("\n");
	
}