单链表固定长度翻转

/***********************************************************

 * Copyright (C), 2012-2013, Cgema Tech. Co., Ltd.

 * FileName : test.c

 * Author : Cgema

 * Version : 1.0 

 * Date : 2013.9.13

 * Description : 单链表的翻转 

 * 原链表长度不知，可能是奇数也可能是偶数

 * 若原链表为：h->1->2->3->4->5->6->7，则：

 * k=2时，将链表翻转为h->2->1->4->3->6->5->7

 * k=3时，将链表翻转为h->3->2->1->6->5->4->7

 * k=4时，将链表翻转为h->4->3->2->1->5->6->7

 * 若原链表为：h->1->2->3->4->5->6->7->8，则：

 * k=4时，将链表翻转为h->4->3->2->1->8->7->6->5

 * Source : 美团网2013笔试题

***********************************************************/



#include<stdio.h>

#include<stdlib.h>



#define k 3

#define length 8

int main()

{

	typedef struct node {

		int num;

		struct node *next;	

	}*List,Node;

	

	int i,n = 0;

	Node *p,*q,*s,*w;

	List head = (Node *)malloc(sizeof(Node));

	

	head->next = NULL;

	q = head;

	for(i=0; i<length; i++)	//create linklist with tail

	{

		p = (Node *)malloc(sizeof(Node));

		p->num = i+1;

		p->next = q->next;

		q->next = p;

		q = p;

		printf("p->num=%d\n",p->num);

	}  

	printf("linklist data init success!\n");

	

	w = head;

	q = p = head->next;

	while(p)

	{

		n++;

		if(n == k)	//opposite linklist operate

		{	

			s = q->next;

			w->next = p->next;

			p->next = NULL;

			p = w->next;

			while(q)

			{

				q->next = w->next;

				w->next = q;

				q = s;

				if(s)	s = s->next;

			}

			q = p;

			if(q)	s = q->next;

			w = head->next;

			while(w->next != p)

				w = w->next;

			n = 0;  

			printf("opposite linklist operate.\n");

		}

		else 

			p = p->next;

	}

	

	if(n != 0)

		printf("最后一组%d不够%d个结点，不可翻转！\n",n,k);

	else 

		printf("全部翻转完毕！\n",n);



	p = head->next;		//free linklist node 

	q = head;

	while(p)	

	{

		printf("p->num=%d\n",p->num);

		free(q);

		q = p;

		p = p->next;

	}  

	return 0;

}