雙向連結清單的建立/測長/列印

與單連結清單相比，每個單元加上前向指針

#include <tchar.h>
#include <iostream>
using namespace std;

typedef struct student{
	int data;
	struct student * next;
	struct student * pre;
} node;

node* create()
{
	node *head, *p, *s;
	int x, cycle = 1;
	head = (node *)malloc(sizeof(node));
	p = head;
	while(cycle)
	{
		cout << "please input the data: ";
		cin >> x;
		cout << endl;
		if( x != 0)
		{
			s = (node *)malloc(sizeof(node));
			s->data = x;
			p->next = s;
			s->pre = p;
			p = s;
		}
		else
		{
			cycle = 0;
		}
		
	}
	p->next = NULL;
	head = head->next;
	head->pre = NULL;
	return head;
}

int length(node *head)
{
	int n = 0;
	node *p;
	p = head;
	while (p != NULL)
	{
		p = p->next;
		n++;
	}
	return n;
}

void print(node *head)
{
	int n;
	node *p;
	p = head;
	n = length(head);
	cout << "There is " << n << " data in list\n" << endl;
	while(p->next != NULL)
	{
		cout << p->data << " -> ";
		p = p->next;
	}
	cout << p->data << endl;
	while(p->pre !=NULL)
	{
		cout << p->data << " -> ";
			p = p->pre;
	}
	cout << p->data << endl;
}

int _tmain(int argc, _TCHAR * argv[])
{
	node *head, *temp;
	head = create();
	print(head);
	return 0;
}