[learning notes] linked list operation

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

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

// Create a linked list 
int list_init(struct list_node *link_list)
{
    
	link_list = (struct list_node*)malloc(sizeof(struct list_node));
	link_list->data = 0;
	link_list->next = NULL;
	return 0;
}

// The linked list adds nodes after a given node 
struct list_node *list_insert(struct list_node *link_list, int data, int n)
{
    
	int i;
	//printf("data = %d\n", data);
	//printf("n = %d\n", n);
	if (link_list == NULL) {
    
		return NULL;
	}
	// Add header node 
	if (n == 0) {
    
		struct list_node *link_head = (struct list_node *)malloc(sizeof(struct list_node));
		link_head->data = data;
		link_head->next = link_list;
		//link_list = link_head;
		return link_head;
	}
	// Add tail node 
	struct list_node *link_tmp = link_list;
	int count = 1;
	for (i = 0; i < n; i++) {
    
		link_tmp = link_tmp->next;
	}
	// Add tail node 
	struct list_node *link_tail_tmp = link_tmp->next;
	if (link_tail_tmp->next == NULL) {
    
		struct list_node *link_tail = (struct list_node *)malloc(sizeof(struct list_node));
		link_tail->data = data;
		link_tail->next = NULL;
		link_tail_tmp->next = link_tail;
		return link_list;
	}
	// Add intermediate nodes 
	struct list_node *link_middle = (struct list_node *)malloc(sizeof(struct list_node));
	link_middle->data = data;
	link_middle->next = link_tail_tmp;
	link_tmp->next = link_middle;
	return link_list;
}

// Delete the specified node 
int link_delete(struct list_node *link_list, int n)
{
    
	int i;
	int count = 0;

	// Delete header node 
	if (n == 0) {
    
		link_list = link_list->next;
		return 0;
	}

	struct list_node *link_tmp = link_list;
	for (i = 0; i < n - 1; i++) {
    
		link_tmp = link_tmp->next;
	}
	//  Delete tail node 
	struct list_node *link_tail = link_tmp->next;
	if (link_tail->next == NULL) {
    
		link_tmp->next = NULL;
		return 0;
	}
	// Delete intermediate nodes 
	struct list_node *link_middle = link_tail->next;
	link_tmp->next = link_middle;
	return 0;
}

int link_show(struct list_node *link_list)
{
    
	while (link_list->next != NULL) {
    
		printf("%d\t", link_list->data);
		link_list = link_list->next;
	}
	printf("%d\n", link_list->data);
	return 0;
}