雙向循環鏈表

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

#define OK 0
#define ERROR -1

#define ElemType int

typedef struct Node
{
	ElemType data;
	Node *prev;		//指向直接前驅
	Node *next;		//指向直接後繼
}Node;

//創建一個帶頭結點的雙向循環鏈表
Node *createList();
//在鏈表的pos位置插入元素e
int insertList(Node *head, int pos, ElemType e);
//刪除鏈表中pos位置的元素，並返回其值
int removeList(Node *head, int pos, ElemType *e);
//遍歷輸出整個鏈表
void traverse(Node *head);

int main()
{
	Node *head = createList();
	
	for (int i=1; i<=500; i++)
	{
		insertList(head, i, i);
	}
	//insertList(head, 2, 501);
	int e;
	removeList(head, 250, &e);
	printf("Remove:%d\n", e);
	traverse(head);

	system("pause");
	return 0;
}

Node *createList()
{
	Node *head = (Node *)malloc(sizeof(Node));
	if (!head)
	{
		printf("內存空間分配失敗，程序將退出\n");
		exit(EXIT_FAILURE);
	}
	head->next = head->prev = head;
	return head;
}

int insertList(Node *head, int pos, ElemType e)
{
	if (!head)
	{
		printf("要插入的鏈表不存在\n");
		return ERROR;
	}
	Node *p = head;
	int i = 1;
	while (p->next != head && i < pos)
	{
		p = p->next;
		i++;
	}
	if (i != pos)
	{
		printf("插入失敗，插入位置不正確\n");
		return ERROR;
	}

	Node *newNode = (Node *)malloc(sizeof(Node));
	if (!newNode)
	{
		printf("內存空間分配失敗，程序將退出\n");
		exit(EXIT_FAILURE);
	}
	newNode->data = e;

	newNode->next = p->next;
	newNode->prev = p;
	p->next->prev = newNode;
	p->next = newNode;

	return OK;
}

int removeList(Node *head, int pos, ElemType *e)
{
	Node *p = head->next;
	int i = 1;
	while (p != head && i < pos)
	{
		p = p->next;
		i++;
	}
	if (i != pos)
	{
		printf("刪除失敗，刪除位置有誤\n");
		return ERROR;
	}
	*e = p->data;
	Node *q = p;
	p->prev->next = p->next;
	p->next->prev = p->prev;
	free(q);
	return OK;
}

void traverse(Node *head)
{
	Node *p = head->next;
	while (p != head)
	{
		printf("%d ", p->data);
		p = p->next;
	}
	printf("\n");
}