双向链表的建立及基本操作

#include<windows.h>
#include<iostream>
#define N 5
using namespace std;
typedef struct DuLnode
{
	int data;    //数据域
	struct DuLnode *prior;  //直接前驱
	struct DuLnode *next;  //直接后继
}DuLnode, *DuLinklist;//双链表的类型定义

DuLinklist InitDulist(int a[N])//初始化双链表
{
	int i;
	DuLinklist L;
	L = (DuLnode*)malloc(sizeof(DuLnode));
	if (L == NULL)
	{
		cout << "error";
		exit(0);
	}
	else L->next = NULL;
	DuLinklist p;
	p = L;
	for (i = 0; i < N; i++)
	{
		DuLinklist q;
		q = (DuLnode*)malloc(sizeof(DuLnode));
		if (q == NULL)
		{
			cout << "error";
			exit(0);
		}
		else q->next = NULL;
		q->data = a[i];
		p->next = q;
		q->prior = p;
		p = q;
	}
	p->next = NULL;
	return L;
}

void putDulist(DuLinklist L)//输出双链表
{
	cout << "当前链表元素为：";
	DuLinklist p;
	p = L->next;
	while (p)
	{
		cout << p->data << " ";
		p = p->next;
	}
	cout << endl;
}

void GetDulinklist(DuLinklist L)//获取链表的第i个元素
{
	int i, j = 0;
	cout << "请输入你要获取第__个元素：";
	cin >> i;
	DuLinklist p;
	p = L->next;
	while (p&&j < i - 1)
	{
		p = p->next;
		j++;
	}
	cout << "第" << i << "个元素为：";
	if (j > i - 1) cout << "error";
	else cout << p->data;
	cout << endl;
}

DuLinklist DeleteDulist(DuLinklist L)//删除链表中的第i个元素
{
	int i, j = 0;
	cout << "请输入你要删除第__个元素";
	cin >> i;
	DuLinklist p, q;
	p = L->next;
	while (p&&j < i - 1)
	{
		p = p->next;
		j++;
	}
	q = L;
	while (q&&q->next != p)
	{
		q = q->next;
	}
	q->next = p->next;
	p->next->prior = q;
	free(p);
	return L;
}

DuLinklist InsertDulist(DuLinklist L)//在第i个元素前插入一个元素
{
	int i, j = 0, x;
	cout << "你要在第__个元素前插入一个值为__的元素，请依次输入：";
	cin >> i >> x;
	DuLinklist p, q;
	p = L->next;
	q = L;
	while (p&&j < i - 1)
	{
		p = p->next;
		j++;
	}
	while (q&&q->next != p)
	{
		q = q->next;
	}
	DuLinklist s;
	s = (DuLnode*)malloc(sizeof(DuLnode));
	if (s == NULL)
	{
		cout << "error";
		exit(0);
	}
	else s->next = NULL;
	s->data = x;
	s->next = p;
	s->prior = q;
	q->next = s;
	p->prior = s;
	return L;
}

int main()
{
	int i, a[N], M;
	DuLinklist L;
	cout << "请输入" << N << "个链表元素：";
	for (i = 0; i < N; i++)
	{
		cin >> a[i];
	}
	L = InitDulist(a);
	while (1)
	{
		Sleep(1000);
		cout << "1:获取链表的第i个元素" << endl;
		cout << "2:在第i个元素前插入一个元素" << endl;
		cout << "3:删除链表中的第i个元素" << endl;
		void putDulist(DuLinklist L);//输出双链表
		cout << "4:输出双链表" << endl;
		cout << "5:退出操作" << endl;
		cout << "请输入你要操作的代号：";
		cin >> M;
		switch (M)
		{
		case 1:
			GetDulinklist(L);
			break;
		case 2:
			InsertDulist(L);
			break;
		case 3:
			DeleteDulist(L);
			break;
		case 4:
			putDulist(L);
			break;
		}
		if (M == 5)break;
	}
	return 0;
}