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
",p->num);
	}  
	printf("linklist data init success!
");
	
	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.
");
		}
		else 
			p = p->next;
	}
	
	if(n != 0)
		printf("最后一组%d不够%d个结点，不可翻转！
",n,k);
	else 
		printf("全部翻转完毕！
",n);

	p = head->next;		//free linklist node 
	q = head;
	while(p)	
	{
		printf("p->num=%d
",p->num);
		free(q);
		q = p;
		p = p->next;
	}  
	return 0;
}