POJ 2503 Babelfish （字典树）

Babelfish

Time Limit : 6000/3000ms (Java/Other) Memory Limit : 131072/65536K (Java/Other)
Total Submission(s) : 53 Accepted Submission(s) : 13
[align=left]Problem Description[/align]
You have just moved from Waterloo to a big city. The people here speak an incomprehensible dialect of a foreign language. Fortunately, you have a dictionary to help you understand them.

[align=left]Input[/align]
Input consists of up to 100,000 dictionary entries, followed by a blank line, followed by a message of up to 100,000 words. Each dictionary entry is a line containing an English word, followed by a space and a foreign language word. No foreign word appears more than once in the dictionary. The message is a sequence of words in the foreign language, one word on each line. Each word in the input is a sequence of at most 10 lowercase letters.

[align=left]Output[/align]
Output is the message translated to English, one word per line. Foreign words not in the dictionary should be translated as "eh".

[align=left]Sample Input[/align]

dog ogday
cat atcay
pig igpay
froot ootfray
loops oopslay

atcay
ittenkay
oopslay

Sample Output

cat
eh
loops

题目大意：在字典中的存入 英语 和对应方言， 然后查找输入的方言 ，如果字典中存在，输出对应的英语；否则输出“eh”
思路有两个：一种是将字典排序后二分查找，另一种是用字典树（前缀树）Trie。第一次写了Trie的代码，参考的《入门经典》，纪念一下

# include<stdio.h>
# include<stdlib.h>
# include<string.h>
# define maxnode 200005
char ans[maxnode][30];    //字典树中结点（方言）对应的英语
//构造字典树
struct Trie{
int ch[maxnode][26];
int val[maxnode];
int sz;        //结点总数
Trie() {sz=1; memset(ch[0],0,sizeof(ch[0])); }    //初始化时只有一个根结点
int idx(char c) { return c-'a';}
void insert(char *s,int v){    //插入字符串
//插入字符串是，附加信息为v。注意v必须为非0，因为0代表“本结点不是单词结点”
int u=0,n=strlen(s);
for(int i=0;i<n;i++){
int c=idx(s[i]);
if(!ch[u][c]){        //结点不存在
memset(ch[sz],0,sizeof(ch[sz]));
val[sz]=0;        //中间结点的附加信息为0
ch[u][c] = sz++;    //新建结点
}
u=ch[u][c];        //往下走
}
val[u] = v;        //字符串最后一个字符的附加信息为v
}
int find(char *s){        //查找字符串
int u=0,n=strlen(s);
for(int i=0;i<n;i++){
int c=idx(s[i]);
if(!ch[u][c]){
return 0;
}
u=ch[u][c];
}
return val[u];
}
}s;
int main(){
int num=1,i,j;
char ss[30];    //要查找字符串
char s1[30],s2[30],s3[60];
//s1英语，s2方言，s3为了检查字典写完而存在的
//输入字典
while(1){
gets(s3);
int len = strlen(s3);
if(len==0)
break;
int flag=0;
for(i=0,j=0;i<len;i++){
if(s3[i]==' ') {s1[j]=0; flag=1; j=0; continue;}
if(flag==0)
s1[j++]= s3[i];
else
s2[j++] = s3[i];
}
s2[j]=0;
strcpy(ans[num],s1);
s.insert(s2,num);
num++;
}
//查找单词
while(scanf("%s",ss)!=EOF){
if(s.find(ss)==0)    //没找到
printf("eh\n");
else
{
printf("%s\n",ans[s.find(ss)]);
}
}
return 0;
}

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