TRIE树在输入法分词的应用

TRIE树,即字典树,可以用于排序、保存大量字符串,在搜索引擎和防火墙中都有着重要的作用。本文使用字典树读取汉语拼音并进行匹配,成功实现了汉语拼音的划分。

先来看看TRIE树的结构:

《TRIE树在输入法分词的应用》

树从root根节点出发,每个节点都有26个子节点(对应各个字母)。不难发现所有n长度的单词组合都在高度为n的TRIE树中。我们把从root节点出发,到某叶子(或节点)的字母组合称为一个单词。

1.定义以下结构体构造TRIE树:

typedef struct TRIE_NODE_ {
    struct TRIE_NODE_ *children[26];
    bool is_word;
} TRIE_NODE;

和我们料想的一样,每个节点都有26个子节点,还有一个标记用于表示root节点到该处是不是一个单词。

2.初始化TRIE树:

static TRIE_NODE* TrieAllocateNode() {
    TRIE_NODE *ret = (TRIE_NODE*) malloc(sizeof(TRIE_NODE));
    if (!ret) exit(1);
    ret->is_word = false;
    memset(ret->children, 0, 26 * sizeof(TRIE_NODE*));
    return ret;
}

通用的树的新节点的建立方法,注意将节点属性初始化为false,并把子节点清空。

3.添加新的单词到树中

void TrieAdd(TRIE_NODE *root, char *text) {
    for (; *text != '\0'; ++text) {                                                   //C中遍历字符串的通用做法
        if (root->children[(*text) - 'a'] == NULL) {
            root->children[(*text) - 'a'] = TrieAllocateNode();                     //把字母直接减去A的ASCLL码值,可以将字母与26个子节点一一对应。
        }
        root = root->children[(*text) - 'a'];                                       //转向下一层树
    }
    root->is_word = true;                                                            //将该单词标为true
}

4.利用深度优先搜索(dfs)分词

void PinyinSolve(TRIE_NODE *root, char *pinyin, char *sp[], int len) {           //字典树root,待处理字符串pinyin,分割点标记数组sp,分割点位置len
    char *p = pinyin;                                                            
    TRIE_NODE *proc = root;                                                      //获取分割指针p和字典中指针proc
    while(true) {
        if (*p == '\0') break;                                                    //字符串处理结束后返回
        if (proc->is_word) {                                                      //是单词时继续递归找出合法子结构
            sp[len] = p;                                                          //每次分割成功都要标记
            PinyinSolve(root, p, sp, len + 1);                                    //递归,检查每种分割
        }
        if (proc->children[(*p) - 'a'] != NULL) {                                 //没到树底就推进指针
            proc = proc->children[(*p) - 'a'];
            p++;
        } else {
            break;
        }
    }
    if (*p == '\0' && proc->is_word == true) {                                     //到结尾且分割方案可行就打印
        sp[len] = p;
        int i;
        for (i = 0; i <= len; ++i) {
            char *mb;
            for (mb = sp[i - 1]; mb < sp[i]; ++mb) {                               //打出分割点间的字符串
                printf("%c", *mb);
            }
            printf("\n");
        }
        printf("----\n");                                                           //给下种分割方案留空
    }
}

典型的DFS的思想,或者DP的思想,递归部分理解有些困难,要注意p的位置和值有效范围,显然展开和回溯过程中p的位置是一样的。

完整代码如下:


//  gcc 下编译通过
//  Copyright (c) 2015年 XiaoJSoft. All rights reserved.
//  字典树词库来自网络
//  In ChestnutHeng's Blog ,If you have any questions ,please contact with <u></u>ChestnutHeng@Gmail.com

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

char *pinyin[] = {"ai","an","ang","ei","ou","ao","ba","bo","bai","bei","bao","ban","ben","bang","beng","bi","bie","biao",
	"bian","bin","bing","pa","po","pai","pao","pou","pan","pen","pang","peng","pi","pie","piao","pian","pin","ping","ma","mo"
	,"me","mai","mao","mou","man","men","mang","meng","mi","mie","miao","miu","mian","min","ming","fa","fo","fei","fou","fan"
	,"fen","fang","feng","da","tu","de","dai","dei","dao","dou","dan","dang","deng","di","die","diao","diu","dian","ding",
	"ta","te","tai","tao","tou","tan","tang","teng","ti","tie","tiao","tian","ting","na","nai","nei","nao","no","nen","nan",
	"nang","neng","ni","nie","niao","niu","nian","nin","niang","ning","la","le","lai","lei","lao","lou","lan","lang","leng",
	"li","lia","lie","liao","liu","lian","lin","liang","ling","ga","ge","gai","gei","gao","gou","gan","gen","gang","geng",
	"ka","ke","kai","kou","kan","ken","kang","keng","ha","he","hai","hei","hao","hou","hen","hang","heng","ji","jia","jie",
	"jiao","jiu","jian","jin","jiang","jing","qi","qia","qie","qiao","qiu","qian","qin","qiang","qing","xi","xia","xie",
	"xiao","xiu","xian","xin","xiang","xing","zha","zhe","zhi","zhai","zhao","zhou","zhan","zhen","zhang","zheng","cha",
	"che","chi","chai","chou","chan","chen","chang","duo","cheng","sha","she","shi","shai","shao","shou","shan","shen",
	"shang","sheng","re","ri","rao","rou","ran","ren","rang","reng","za","ze","zi","zai","zao","zou","zang","zeng",
	"ca","ce","ci","cai","cao","cou","can","cen","cang","ceng","sa","se","si","sai","sao","sou","san","sen","sang",
	"seng","ya","yao","you","yan","yang","yu","ye","yue","yuan","yi","yin","yun","ying","wa","wo","wai","wei","wan",
	"wen","wang","weng","wu",NULL
};                  //这个字典不全, = =坑爹的,不是我写的啊。

typedef struct TRIE_NODE_ {
    struct TRIE_NODE_ *children[26];
    bool is_word;
} TRIE_NODE;

#define MAX_LEN 128

char g_Input[MAX_LEN + 1];

static TRIE_NODE* TrieAllocateNode() {
    TRIE_NODE *ret = (TRIE_NODE*) malloc(sizeof(TRIE_NODE));
    if (!ret) exit(1);
    ret->is_word = false;
    memset(ret->children, 0, 26 * sizeof(TRIE_NODE*));
    return ret;
}

void TrieAdd(TRIE_NODE *root, char *text) {
    for (; *text != '\0'; ++text) {
        if (root->children[(*text) - 'a'] == NULL) {
            root->children[(*text) - 'a'] = TrieAllocateNode();
        }
        root = root->children[(*text) - 'a'];
    }
    root->is_word = true;
}


void PinyinSolve(TRIE_NODE *root, char *pinyin, char *sp[], int len) {
    char *p = pinyin;
    TRIE_NODE *proc = root;
    while(true) {
        if (*p == '\0') break;
        if (proc->is_word) {
            sp[len] = p;
            PinyinSolve(root, p, sp, len + 1);
        }
        if (proc->children[(*p) - 'a'] != NULL) {
            proc = proc->children[(*p) - 'a'];
            p++;
        } else {
            break;
        }
    }
    if (*p == '\0' && proc->is_word == true) {
        sp[len] = p;
        int i;
        for (i = 0; i <= len; ++i) {
            char *mb;
            for (mb = sp[i - 1]; mb < sp[i]; ++mb) {
                printf("%c", *mb);
            }
            printf("\n");
        }
        printf("----\n");
    }
}


int main(int argc, const char * argv[]) {
    TRIE_NODE *root = TrieAllocateNode();
    char **ptr;
    for (ptr = pinyin; *ptr != NULL; ++ptr) {
        TrieAdd(root, *ptr);
    }
    
    scanf("%s", g_Input);
    char *buffer[999];
    buffer[0] = g_Input;
    PinyinSolve(root, g_Input, buffer + 1, 0);
    printf("OK\n");
    
    return 0;
}

    原文作者:Trie树
    原文地址: https://blog.csdn.net/u011477670/article/details/46523507
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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