HDU 1075 What are you talking about(trie树)

#include<stdio.h>
#include<malloc.h>
#include<string.h>
#define MAXNUM 27
typedef struct tnode
{
int mark,count;
tnode *next[MAXNUM];
char words[20];

}tnode;
tnode *root;
char result[20];
void init()
{
int i;
root=(tnode*)malloc(sizeof(tnode));
for(i=0;i<MAXNUM;i++)
root->next[i]=NULL;
root->mark=0;

}
void  insert(char words[20],char *str)
{
tnode *r=root,*child;
int i,flag=0;
while(*str!='\0')
{
if(r->next[*str-'a']==NULL)
{   flag=1;
child=(tnode*)malloc(sizeof(tnode));
for(i=0;i<MAXNUM;i++)
child->next[i]=NULL;
child->mark=0;
child->count=0;
r->next[*str-'a']=child;

}
r->next[*str-'a']->count++;
r=r->next[*str-'a'];
str++;

}

r->mark=1;
strcpy(r->words,words);

}

void search(char *s)
{
tnode *r=root;
int i,len;
len=strlen(s);
i=0;
//就是这个地方，我之前写的是while(r->next[*str-'a']!=NULL),理所当然的RE了
for(i=0;i<len;i++)
{
if(r->next[*s-'a']==NULL)return;
if(i==len-1&&(r->next[*s-'a']->mark==1))  {strcpy(result,r->next[*s-'a']->words);return;}
r=r->next[*s-'a'];
s++;

}
return;
}

int main()
{
char str[3100],words[20],temp[3100];
int i,j,flag,len;
init();
scanf("START");
while(strcmp(str,"END")!=0)
{

scanf("%s",words);
if(strcmp(words,"END")==0)break;
scanf("%s",str);
insert(words,str);

}
gets(str);
scanf("START");
gets(str);
gets(temp);
while((strcmp(temp,"END")!=0))
{

i=0;
len=strlen(temp);
while(i<len)
{
j=0;
flag=0;
while((temp[i]>='a'&&temp[i]<='z'))

{
flag=1;
str[j++]=temp[i++];

}
if(flag)
{
str[j]='\0';
result[0]='\0';
search(str);
if(result[0]=='\0')
printf("%s",str);
else  printf("%s",result);
}
printf("%c",temp[i]);
i++;
}
printf("\n");
gets(temp);

}

return 0;
}