C语言双向循环链表基本操作

#include<iostream>
#include<cstring>
#include<stdlib.h>
using namespace std;

typedef struct DLnode
{
	int data;
	struct DLnode *prior;
	struct DLnode *next;
}DLnode,*Dlnode;

void InitDlist(Dlnode &head) //循环双向初始化 
{
	head=(Dlnode)malloc(sizeof(DLnode));
	head->prior=head;
	head->next=head;
	cout<<"初始化成功！"<<endl;
}

void InsertDlist(DLnode *head,int i) //头插法 
{
	Dlnode p=NULL;
	p=(DLnode *)malloc(sizeof(DLnode));
	if(!p)
	{
		cout<<"对不起，无法分配更多的内存！"<<endl;
		return;
	}
	p->data=i;
	p->next=head->next;
	p->next->prior=p;
	p->prior=head;
	head->next=p;
}

int EmptyDlist(Dlnode head)
{
	if(head->prior==head&&head->next==head) //双向判空
	return 1;
	
	return 0;
}

int LengthDlist(Dlnode head)
{
	DLnode *p=NULL;
	int len=0;
	if(EmptyDlist(head))
	return 0;
	p=head->next;
	while(p!=head)
	{
		len++;
		p=p->next;
	}
	return len;
}

int DeleteDlist(DLnode *head,int x)
{
	DLnode *p=NULL;
	int i=1;
	p=head->next;
	if(EmptyDlist(head))
	{
		cout<<"对不起，链表为空！"<<endl;
		return 0; 
	}
	if(x>LengthDlist(head)||x<=0)
	{
		cout<<"对不起，删除的位置不合适！"<<endl;
		return 0; 
	}
	while(i<x)
	{
		p=p->next;
		i++;
	}
	p->prior->next=p->prior->next->next;
	p->prior->next->prior=p->prior;
	return p->data;
}

void InsearchDlist(Dlnode head,int x)
{
	DLnode *p=NULL;
	int len=1;
	if(EmptyDlist(head))
	{
		cout<<"对不起链表是空！"<<endl;
		return;
	}
	p=head->next;
	while(p!=head)
	{
		if(p->data==x)
		{
			cout<<"你查找的元素在第"<<len<<"个"<<endl;
			return;
		}
		p=p->next;
		len++;
	}
	cout<<"你所找的元素不存在！"<<endl;
	return;
}

void ModifyDlist(DLnode *head,int local,int x)
{
	DLnode *p=NULL;
	int len=1;
	p=head->next;
	while(len<local)
	{
		p=p->next;
		len++;
	}
	p->data=x;
	cout<<"修改成功！"<<endl;
	return;
}

void DestoryDlist(Dlnode head)
{
	Dlnode p=head->next;
	while(p!=head)
	{
		p->prior->next=p->next;
		p->next->prior=p->prior;
		p=head->next;
	}
	cout<<"销毁成功！"<<endl;
}

void PrintDlist(Dlnode head)
{
	Dlnode p=head->next;
	if(EmptyDlist(head))
	{
		cout<<"链表是空的，无法输出链表！"<<endl;
		return;
	}
	while(head!=p)
	{
		cout<<p->data<<' ';
		p=p->next;
	}
	cout<<endl;
	return;
}

void instruction(Dlnode head)
{
	cout<<"1. 初始操作"<<endl;
	cout<<"2. 新增操作"<<endl;
	cout<<"3. 删除操作"<<endl;
	cout<<"4. 查找操作"<<endl;
	cout<<"5. 修改操作"<<endl;
	cout<<"6. 销毁操作"<<endl;
	cout<<"7. 求长操作"<<endl;
	cout<<"8. 输出操作"<<endl;
	cout<<"9. 退出程序"<<endl; 
	cout<<"请输入要完成的指令：";
	int n,x,i,local,len;
	cin>>n;
	if(n<1||n>9)
	{
		cout<<"对不起，你的操作无效！"<<endl;
		exit(0);
	}
	switch(n)
	{
		case 1:
			InitDlist(head);
			cout<<"接下来完成建表操作"<<endl;
			cout<<"请输入你要添加的元素的个数：";
			cin>>x;
			while(x--)
			{
				cout<<"请输入一个值："; 
				cin>>i;
				InsertDlist(head,i);
			} 
			break;
		case 2:
			if(!head)
			{
				cout<<"对不起，请先初始化！"<<endl;
				break;
			}
			cout<<"请输入你要添加的元素的个数：";
			cin>>x;
			while(x--)
			{
				cout<<"请输入一个值："; 
				cin>>i;
				InsertDlist(head,i);
			} 
			break;
		case 3:
			cout<<"请输入删除结点的位置：";
			cin>>x;
			DeleteDlist(head,x);
			break;
		case 4:
			cout<<"请输入你要查找的元素：";
			cin>>x;
			InsearchDlist(head,x);
			break;
		case 5:
			if(EmptyDlist(head))
			{
				cout<<"对不起，链表为空！"<<endl;
				break;
			}
			cout<<"请输入你要改变的元素的位置：";
			do
			{
				cin>>local;
				if(local<1||local>LengthDlist(head))
				cout<<"对不起，你输入的元素不在区域内！请重新输入："; 
			}while(local<1||local>LengthDlist(head));
			cout<<"请输入修改后的值：";
			cin>>x;
			ModifyDlist(head,local,x);
			break;
		case 6:
			DestoryDlist(head);
			break;
		case 7:
			len=LengthDlist(head);
			cout<<"当前链长为："<<len<<endl;
			break;
		case 8:
			PrintDlist(head);
			break;
		case 9:
			return;
		default:
			instruction(head);
			break;
	}
	instruction(head);
}

int main()
{
	Dlnode head=NULL;
	instruction(head); //实现不同功能的函数 
	return 0;
}