3.单词压缩存储——单向链表

如果采用单链表保存单词，可采用如下办法压缩存储空间。如果两个单词的后缀相同，则可以用同一个存储空间保存相同的后缀。例如，原来分别采用单链表保存的单词Str1“loading”和单词Str2“being”，经过压缩后的存储形式如下。

单词压缩

请设计一个高效的算法完成两个单链表的压缩存储。

要求：阅读预设代码，编写函数SNODE * ziplist( SNODE * head1, SNODE * head2 )
ziplist的功能是：在两个串链表中，查找公共后缀，若有公共后缀，则压缩 并返回指向公共后缀的指针；否则返回NULL。

说明：本题目有预设代码，只要提交你编写的函数即可。

预设代码

/* PRESET CODE BEGIN - NEVER TOUCH CODE BELOW */

#include <stdio.h>
#include <stdlib.h>

typedef struct sdata
{  char  data;
   struct sdata *next;
} SNODE;

void setlink( SNODE *, char * ), outlink( SNODE * );
int listlen( SNODE * );
SNODE * ziplist( SNODE *, SNODE * );
SNODE * findlist( SNODE *, SNODE * );

int main( )
{	SNODE * head1, * head2, *head;
	char str1[100], str2[100];

	gets( str1 );
	gets( str2 );

	head1 = (SNODE *) malloc( sizeof(SNODE) );
	head2 = (SNODE *) malloc( sizeof(SNODE) );
	head = (SNODE *) malloc( sizeof(SNODE) );
	head->next = head1->next = head2->next = NULL;

	setlink( head1, str1 );
	setlink( head2, str2);

	head->next = ziplist( head1, head2 );

	head->next = findlist( head1, head2 );
	outlink( head );
	return 0;
}

void setlink( SNODE *head, char *str )
{
	SNODE *p ;

	while ( *str != '\0' )
	{   p  = ( SNODE * ) malloc( sizeof( SNODE ) );
		p->data = *str;
		p->next = NULL;
		str++;
		head->next = p;
		head = p;
	}
	return;
}

void outlink( SNODE * head )
{	while ( head->next != NULL )
	{
		printf( "%c", head -> next -> data );
		head = head -> next;
	}
	printf("\n");
	return;
}

int listlen( SNODE * head )
{
	int len=0;
	while ( head->next != NULL )
	{
		len ++;
		head = head->next;
	}
	return len;
}

SNODE * findlist( SNODE * head1, SNODE * head2 )
{
	int m, n;
	SNODE *p1=head1, *p2=head2;

	m = listlen( head1 );
	n = listlen( head2 );
	while  ( m > n )
	{	p1 = p1->next;
		m--;
	}
	while  ( m < n )
	{	p2 = p2->next;
		n--;
	}

	while( p1->next != NULL && p1->next != p2->next )
	{
		p1 = p1->next;
		p2 = p2->next;
	}
	return p1->next;
}
/* Here is waiting for you!     */
/*
  SNODE * ziplist( SNODE * head1, SNODE * head2 )
  {
  }
*/

/* PRESET CODE END - NEVER TOUCH CODE ABOVE */

测试用例
in:
abcdef
dbdef
out:
def↵

SNODE * ziplist( SNODE * head1, SNODE * head2 )
{
	SNODE *p1=head1,*p2=head2;
	int len1=listlen(head1),len2=listlen(head2);
	while(len1>len2)
	{
		p1=p1->next;
		len1--;
	}
	while(len1<len2)
	{
		p2=p2->next;
		len2--;
	}
	SNODE *t1=p1,*t2=p2;
	while(p1->next->next!=NULL)
	{
		if(p1->next->data!=p2->next->data)
		{
			t1=p1->next;
			t2=p2->next;
		}
		p1=p1->next;
		p2=p2->next;
	}
	if(p1->next->data!=p2->next->data)
		return NULL;
	else
	{
		t2->next=t1->next;
		return t2->next;
	}
}