单词拼写检查器
哈哈，一个有趣的问题，写一个单词拼写检查器，在微薄上看到的，各路大神用各种语言实现～～
学习了一下人家代码：表示各种malloc,realloc, char **, 等等。。。。自己写静态写习惯了
现在看动态都有点不习惯了。。
我写了注释代码：
原文：http://marcelotoledo.com/2007/08/10/how-to-write-a-spelling-corrector/
View Code
/* * spell.c --- spell corrector * * Copyright (C) 2007 Marcelo Toledo <marcelo@marcelotoledo.org> * * Version: 1.0 * Keywords: spell corrector * Author: Marcelo Toledo <marcelo@marcelotoledo.org> * Maintainer: Marcelo Toledo <marcelo@marcelotoledo.org> * URL: http://www.marcelotoledo.org * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA * * Commentary: * * See http://www.marcelotoledo.org. * * Code: */ #include <stdio.h> #include <stdlib.h> #include <string.h> #include <ctype.h> #include <search.h> #include <sys/types.h> #include <sys/stat.h> #include <unistd.h> #define DICTIONARY "./big.txt" #define DICT_SZ 3000000 const char delim[] = ".,:;`/\"+-_(){}[]<>*&^%$#@!?~/|\\=1234567890 \t\n"; //读取语义材料时，识别每个单词，分割符为delim数组内的字符 const char alphabet[] = "abcdefghijklmnopqrstuvwxyz";//26个字符，对与每一个位置，都要替换，插入～～ //将单词转为小写 static char *strtolower(char *word) { char *s; for (s = word; *s; s++) *s = tolower(*s); return word; } /* hsearch,hash table, typedef struct entry { char *key; void *data; }ENTRY; */ static ENTRY *find(char *word) { ENTRY e; e.key = word; return hsearch(e, FIND); } //如果此关键字存在就次数++,不存在就返回0 static int update(char *word) { ENTRY *e = find(word); if (!e) return 0; e->data++; return 1; } //读取语义材料的每个单词，并将其加入HASH表，建立正确的统计模型 static int read_file(ENTRY dict) { char *file, *word, *w; FILE *fp = fopen(DICTIONARY, "r"); struct stat sb; if (!fp) return 0; if (stat(DICTIONARY, &sb)) return 0; file = malloc(sb.st_size); if (!file) { fclose(fp); return 0; } fread(file, sizeof(char), sb.st_size, fp); word = strtok(file, delim); while(word != NULL) { w = strtolower(strdup(word)); if (!update(w)) { dict.key = w; dict.data = 0; hsearch(dict, ENTER); } word = strtok(NULL, delim); } free(file); fclose(fp); return 1; } //将str从offset开始的limit个字节复制成一个新字符串，并返回这个字符串 static char *substr(char *str, int offset, int limit) { char *new_str; int str_size = strlen(str); if ((limit > str_size) || ((offset + limit) > str_size) || (str_size < 1) || (limit == 0)) return NULL; new_str = malloc(limit+1 * sizeof(char)); if (!new_str) return NULL; strncpy(new_str, str+offset, limit); *(new_str + limit) = '\0'; return new_str; } //连接字符串1和字符串2 static char *concat(char *str1, char *str2) { if (!str1) { str1 = malloc(sizeof(char)); *str1 = '\0'; } if (!str2) { str2 = malloc(sizeof(char)); *str2 = '\0'; } str1 = realloc(str1, strlen(str1) + strlen(str2) + 1); return strcat(str1, str2); } //删除一个字符 static int deletion(char *word, char **array, int start_idx) { int i, word_len = strlen(word); for (i = 0; i < word_len; i++) array[i + start_idx] = concat(substr(word, 0, i), substr(word, i+1, word_len-(i+1))); return i; } //交换i位置与i+1位置 static int transposition(char *word, char **array, int start_idx) { int i, word_len = strlen(word); for (i = 0; i < word_len-1; i++) array[i + start_idx] = concat(concat(substr(word, 0, i), substr(word, i+1, 1)), concat(substr(word, i, 1), substr(word, i+2, word_len-(i+2)))); return i; } //将i位置替换26个字符 static int alteration(char *word, char **array, int start_idx) { int i, j, k, word_len = strlen(word); char c[2] = { 0, 0 }; for (i = 0, k = 0; i < word_len; i++) for (j = 0; j < sizeof(alphabet); j++, k++) { c[0] = alphabet[j]; array[start_idx + k] = concat(concat(substr(word, 0, i), (char *) &c), substr(word, i+1, word_len - (i+1))); } return k; } //在i位置插入26个字符 static int insertion(char *word, char **array, int start_idx) { int i, j, k, word_len = strlen(word); char c[2] = { 0, 0 }; for (i = 0, k = 0; i <= word_len; i++) for (j = 0; j < sizeof(alphabet); j++, k++) { c[0] = alphabet[j]; array[start_idx + k] = concat(concat(substr(word, 0, i), (char *) &c), substr(word, i, word_len - i)); } return k; } //返回1次编辑，将产生多少行，也就是需要多少个一维array数组 static int edits1_rows(char *word) { register int size = strlen(word); return (size) + // deletion (size - 1) + // transposition (size * sizeof(alphabet)) + // alteration (size + 1) * sizeof(alphabet); // insertion } //对字符串四种操作，枚举每一种可能，结果保存在array数组中 static char **edits1(char *word) { int next_idx; char **array = malloc(edits1_rows(word) * sizeof(char *)); if (!array) return NULL; next_idx = deletion(word, array, 0); next_idx += transposition(word, array, next_idx); next_idx += alteration(word, array, next_idx); insertion(word, array, next_idx); return array; } //如果存在该单词，就返回1 static int array_exist(char **array, int rows, char *word) { int i; for (i = 0; i < rows; i++) if (!strcmp(array[i], word)) return 1; return 0; } //2次编辑 static char **known_edits2(char **array, int rows, int *e2_rows) { int i, j, res_size, e1_rows; char **res = NULL, **e1; for (i = 0, res_size = 0; i < rows; i++) { e1 = edits1(array[i]); e1_rows = edits1_rows(array[i]); for (j = 0; j < e1_rows; j++) if (find(e1[j]) && !array_exist(res, res_size, e1[j])) { res = realloc(res, sizeof(char *) * (res_size + 1)); res[res_size++] = e1[j]; } } *e2_rows = res_size; return res; } //找单词出现次数最多的一个单词 static char *max(char **array, int rows) { char *max_word = NULL; int i, max_size = 0; ENTRY *e; for (i = 0; i < rows; i++) { e = find(array[i]); if (e && ((int) e->data > max_size)) { max_size = (int) e->data; max_word = e->key; } } return max_word; } //释放动态申请的内存 static void array_cleanup(char **array, int rows) { int i; for (i = 0; i < rows; i++) free(array[i]); } //返回最接近或正确的单词 static char *correct(char *word) { char **e1, **e2, *e1_word, *e2_word, *res_word = word; int e1_rows, e2_rows; if (find(word)) return word; e1_rows = edits1_rows(word); if (e1_rows) { e1 = edits1(word); e1_word = max(e1, e1_rows); if (e1_word) { array_cleanup(e1, e1_rows); free(e1); return e1_word; } } e2 = known_edits2(e1, e1_rows, &e2_rows); if (e2_rows) { e2_word = max(e2, e2_rows); if (e2_word) res_word = e2_word; } array_cleanup(e1, e1_rows); array_cleanup(e2, e2_rows); free(e1); free(e2); return res_word; } int main(int argc, char **argv) { char *corrected_word; ENTRY dict; hcreate(DICT_SZ); if (!read_file(dict)) return -1; corrected_word = correct(argv[1]); if (strcmp(corrected_word, argv[1])) { printf("Did you mean \"%s\"?\n", corrected_word); } else { printf("\"%s\" is correct!\n", argv[1]); } return 0; }
