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

typedef char DataType;
typedef struct Node
{
	DataType data;
	struct Node *prior;
	struct Node *next;
}DListNode,*DLinkList;
DListNode* GetElem(DLinkList head, int i);
void PrintDList(DLinkList head);
int CreateDList(DLinkList head, int n);
int InsertDList(DLinkList henad, int i, char e);

int InitDList(DLinkList *head)
{
	*head = (DLinkList)malloc(sizeof(DListNode));
	if (!head)
		return -1;
	(*head)->next = *head;  //使頭結點的prior和next指標指向自己
	(*head)->prior = *head;
	return 1;
}
int CreateDList(DLinkList head, int n)
{
	DListNode *s, *q;
	int i;
	DataType e;
	q = head;
	for (i = 1; i <= n; i++)
	{
		printf("輸入%d個元素", i);
		e = getchar();
		s = (DListNode*)malloc(sizeof(DListNode));
		s->data = e;//將新生成的結點插入雙向迴圈連結串列
		s->next = q->next;
		q->next = s;
		s->prior = q;
		head->prior = s;//這裡注意頭結點的prior指向新插入的結點
		q = s;  //q始終指向最後一個結點
		getchar();
	}
	return 1;
}
int InsertDList(DLinkList head, int i, DataType e)
{
	DListNode *p, *s;
	p = GetElem(head, i);		//查詢連結串列中第i個結點
	if (!p)
		return 0;
	s = (DListNode*)malloc(sizeof(DListNode));
	if (!s)
		return -1;
	s->data = e;		//將s結點插入到雙向連結串列中
	s->prior = p->prior;
	p->prior->next = s;
	s->next = p;
	p->prior = s;
	return 1;
}

DListNode* GetElem(DLinkList head ,int i)
{
	DListNode *p;
	int j;
	p = head->next;
	j = 1;
	while (p != head && j < i)
	{
		p=p->next;
		j++;
	}
	if (p == head || j>i)   //如果位置不整確，返回NULL
		return NULL;
	return p;
}
void main()
{
	DLinkList h;
	int n, pos;
	char e;
	InitDList(&h);
	printf("輸入元素個數：");
	scanf("%d", &n);
	getchar();
	CreateDList(h, n);
	printf("連結串列中的元素：");
	PrintDList(h);
	printf("請輸入元素以及位置：");
	scanf("%c", &e);
	getchar();
	scanf("%d", &pos);
	InsertDList(h, pos, e);
	printf("插入元素後連結串列中的元素：");
	PrintDList(h);
}
void PrintDList(DLinkList head)  //輸出迴圈雙鏈表中的每一個元素
{
	DListNode *p;
	p = head->next;
	while (p != head)
	{
		printf("%c", p->data);
		p = p->next;
	}
	printf("\n");
}