一 描述

Trie，又称单词查找树或键树，是一种树形结构，是一种哈希树的变种。典型应用是用于统计和排序大量的字符串（但不仅限于字符串），所以经常被搜索引擎系统用于文本词频统计。它的优点是：最大限度地减少无谓的字符串比较，查询效率比哈希表高。

二 

    本题是要根据词典，来翻译句子，数据结构

struct trie_node
{
    char trans[11];//翻译
    bool is_has;   //是否在词典存在
    struct trie_node *next[num];//儿子节点

};

三 代码

#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <ctype.h>
#define num 26
struct trie_node
{
    char trans[11];
    bool is_has;
    struct trie_node *next[num];

};
static struct trie_node root;
void insert(char *s, char* t)
{
    struct trie_node *curr = &root;
    struct trie_node *newnode = NULL;
    while(*s)
    {
        if (curr->next[*s-'a'] == NULL)
        {
            newnode = (struct trie_node*) malloc(sizeof(struct trie_node));
            memset(newnode, 0, sizeof(struct trie_node));
            curr->next[*s-'a'] = newnode;
        }
        curr = curr->next[*s-'a'];
        ++s;
    }
    curr->is_has = true;
    strcpy(curr->trans, t);

}
char* find(char* s)
{
    struct trie_node *curr = &root;
    char* t =s;
    while(*t)
    {
        if (curr->next[*t-'a'] != NULL)
        {
            curr = curr->next[*t-'a'];
            ++t;
        }
        else
            return s;
    }
    if (curr->is_has)
		return curr->trans;
    else
		return s;
}
int main()
{
    freopen("in.txt", "r", stdin);
    char s1[1003];
    char s2[1003];
    scanf("%s", s1);
    while (scanf("%s", s1) && strcmp(s1, "END") != 0)
    {
        scanf("%s", s2);
        insert(s2, s1);
    }
    getchar();
    gets(s1);
    int c;

    int ith = 0;
    while ( (c = getchar()) != 'E')
    {
    	if (c >= 'a' && c <= 'z')
			s2[ith++] = c;
        else
        {
            s2[ith] = '\0';
            if (ith != 0)
                printf("%s", find(s2));
            printf("%c", c);
            ith = 0;
        }
    }


    return 0;
}