Babelfish（字典树）

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本文介绍了一个基于字典树实现的简单翻译程序——Babelfish。该程序能够通过预先建立的单词对照表，将一种语言的文本转换成另一种语言。主要讨论了如何构建字典树以高效地进行翻译，并提供了完整的源代码。

Babelfish

Time Limit: 3000MS		Memory Limit: 65536K
Total Submissions: 29680		Accepted: 12848

Description

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.

Input

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.

Output

Output is the message translated to English, one word per line. Foreign words not in the dictionary should be translated as "eh".

Sample Input

dog ogday
cat atcay
pig igpay
froot ootfray
loops oopslay

atcay
ittenkay
oopslay

Sample Output

cat
eh
loops

Hint

Huge input and output,scanf and printf are recommended.

Source

Waterloo local 2001.09.22

题意：

给出一系列单词和译文，空行后开始询问译文，每个询问输出一个答案，如果译文能输出对应的单词，则输出这个单词，不能则输出 eh。

思路：

字典树。将对应单词输入到译文最后一个字母中，每次询问则查找字典树即可。

AC：

#include<cstdio>
#include<string.h>
using namespace std;

typedef struct no
{
    struct no *next[30];
    char sen[15];
}node;

node *creat_node()
{
    node *p = new node;
    for(int i = 0;i < 30;i++)
        p -> next[i] = NULL;
    memset(p -> sen,0,sizeof(p -> sen));
    return p;
}

void insert_str(char *str,char *vab,node *head)
{
    int len = strlen(str);
    node *p = head;
    for(int i = 0;i < len;i++)
    {
        int c = str[i] - 'a';
        if(p -> next[c] == NULL)    
           p -> next[c] = creat_node();
        p = p -> next[c];
    }
    strcpy(p -> sen,vab);
}

void search_str(char *str,node *head)
{
    int len = strlen(str),i;
    node *p = head;
    for(i = 0;i < len;i++)
    {
        int c = str[i] - 'a';
        if(p -> next[c] == NULL) break;
        p = p -> next[c];
    }
//除了判断i < len以外，还要判断长度，因为当这个译文为某字典译文的前缀时，最后一个字母没有存到单词信息
    if(i < len || !strlen(p -> sen)) printf("eh\n");
    else                             printf("%s\n",p -> sen);
}

int main()
{
    char str[3005],vab[30],tra[30];
    node *head = creat_node();

    while(gets(str) && strlen(str))
    {
        int temp = 0,k = 0;
        memset(vab,0,sizeof(vab));
        memset(tra,0,sizeof(tra));
        for(int i = 0;i < strlen(str);i++)
        {
            if(str[i] == ' ')
            {
                temp = 1;
                vab[k] = '\0';
                k = 0;
                continue;
            }
            if(!temp)   vab[k++] = str[i];
            else        tra[k++] = str[i];
        }
        tra[k] = '\0';
        insert_str(tra,vab,head);
    }

    while(gets(str))
    {
        search_str(str,head);
    }
    return 0;
}