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

typedef struct Item
{
	int num;
	float price;
	struct Item* next;
}*PItem;

void Error_Msg(char*);
void AddNewItem(PItem *, PItem *, int, int, float);
void CreateList(PItem *, PItem *, FILE *);
void PrintItem(PItem);
void PrintList(PItem, char*);
void WriteListToFile(PItem, FILE *);
void DeleteList(PItem *);

int main()
{
	int a, n;
	float b;
	PItem head = NULL, tail = NULL;
	FILE *in = fopen("input_price.txt", "rt");
	if (in == NULL)
	{
		Error_Msg("input file is wrong");
	}
	CreateList(&head, &tail, in);
	PrintList(head, "\nThe Old List:\n");
	printf("\n\nEnter a number and the price\n");
	scanf("%d%f", &a, &b);
	printf("\nEnter a place for the new item:");
	scanf("%d", &n);
	AddNewItem(&head, &tail, n, a, b);
	PrintList(head, "\nThe New List:\n");
	fclose(in);



	//WriteListToFile(head, in);
	//DeleteList(&head);
	tail = NULL;
	return 0;
}
//-------------------------------------------------------------------
void Error_Msg(char*msg)
{
	printf("\n%s", msg);
	exit(1);
}
//-------------------------------------------------------------------
void CreateList(PItem *head, PItem *tail, FILE *f)
{
	int a;
	float b;
	PItem temp;
	while (fscanf(f, "%d %f", &a, &b) == 2)
	{
		temp = (PItem)malloc(sizeof(struct Item));
		if (temp == NULL)
		{
			DeleteList(head);
			Error_Msg("Memmory!");
		}
		temp->num = a;
		temp->price = b;
		temp->next = NULL;
		if (*head == NULL)
			*head = temp;
		else
			(*tail)->next = temp;
		*tail = temp;
	}
}
//-------------------------------------------------------------------
void PrintItem(PItem node)
{
	printf("%d,%.1f-->", node->num, node->price);
}
//-------------------------------------------------------------------
void PrintList(PItem head, char* title)
{
	printf("%s", title);
	while (head)
	{
		PrintItem(head);
		head = head->next;
	}
}
//-------------------------------------------------------------------
void DeleteList(PItem *head)
{
	PItem tmp = *head;
	while (*head)
	{
		tmp = *head;
		*head = (*head)->next;
		free(tmp);
	}
}
//-------------------------------------------------------------------
void AddNewItem(PItem *head, PItem *tail, int n, int a, float b)
{
	PItem* prev,next;
	PItem item;
	prev=NULL; next = NULL; item = NULL;
	int i;
	item = (PItem)malloc(sizeof(struct Item));
	item->num = a;
	item->price = b;
	prev = head;
	for (i = 0; i < n; i++)
	{
		prev = (**prev).next;
		if (i == n-1)
		{
			next = prev->next->next;
			break;
		}
	}
	prev->next = item;
	item->next = next;
	return;
}