c - 用普通 C 将文本文件读入数组

Question

有没有办法用纯 C 将文本文件读入一维数组？这是我尝试过的(我正在写刽子手):

int main() {
    printf("Welcome to hangman!");

    char buffer[81];
    FILE *dictionary;
    int random_num;
    int i;
    char word_array[80368];

    srand ( time(NULL) );

    random_num = rand() % 80368 + 1;
    dictionary = fopen("dictionary.txt", "r");

    while (fgets(buffer, 80, dictionary) != NULL){
        printf(buffer); //just to make sure the code worked;
        for (i = 1; i < 80368; i++) {
            word_array[i] = *buffer;
        }
    }

    printf("%s, \n", word_array[random_num]);
    return 0;
}

这里有什么问题吗？

Answer 1

尝试改变一些东西；

首先；您正在存储一个字符。 word_array[i] = *buffer; 表示将单个字符(行中/缓冲区中的第一个字符)复制到 word_array 中的每个(和每个)单字符槽中。

其次，您的数组将包含 80K 个字符，而不是 80K 个单词。假设那是你的字典文件的长度，你不能用那个循环把它全部放在那里。

I'm assuming you have 80,368 words in your dictionary file. That's about 400,000 words less than /usr/share/dict/words on my workstation, though, but sounds like a reasonable size for hangman…

如果出于某种原因你有意想要一个一维数组，你必须做以下三件事之一:

• 假设您在大型机上，每个单词使用 80 个字符:

    char word_array[80368 * 80];
  
  memcpy (&(word_array[80 * i]), buffer, 80);
  

• 在一个巨大的缓冲区中创建一个并行数组，其中索引指向每一行的开头

     int last_char = 0;
     char* word_start[80368];
     char word_array[80368 * 80];
     for ( … i++ ) {
         memcpy (&word_array[last_char], buffer, strlen(buffer));
         word_start[i] = last_char;
         last_char += strlen(buffer);
     }
  

• 切换到使用指向 char 的指针数组，每个槽一个字。

    char* word_array[80368];
  
    for (int i = 0; i < 80368, i++) {
         fgets (buffer, 80, dictionary);
         word_array[i] = strdup (buffer);
    }
  

我推荐后者，否则您必须猜测最大大小或在阅读时浪费大量 RAM。 (如果你的平均单词长度大约是 4-5 个字符，就像在英语中一样，你平均每个单词浪费 75 个字节。)

我还建议动态分配 word_array:

   int max_word = 80368;
   char** word_array = malloc (max_word * sizeof (char*));

...如果您的字典大小发生变化，这可以让您更安全地阅读:

   int i = 0;
   while (1) {
        /* If we've exceeded the preset word list size, increase it. */
        if ( i > max_word ) {
            max_word *= 1.2; /* tunable arbitrary value */
            word_array = realloc (word_array, max_word * sizeof(char*));
        }
        /* Try to read a line, and… */
        char* e = fgets (buffer, 80, dictionary);
        if (NULL == e) { /* end of file */
            /* free any unused space */
            word_array = realloc (word_array, i * sizeof(char*));
            /* exit the otherwise-infinite loop */
            break;
        } else {
            /* remove any \r and/or \n end-of-line chars */
            for (char *s = &(buffer[0]); s < &(buffer[80]); ++s) {
               if ('\r' == *s || '\n' == *s || '\0' == *s) {
                  *s = '\0'; break;
               }
            }
            /* store a copy of the word, only, and increment the counter.
             * Note that `strdup` will only copy up to the end-of-string \0,
             * so you will only allocate enough memory for actual word
             * lengths, terminal \0's, and the array of pointers itself. */
            *(word_array + i++) = strdup (buffer);
        }
    }
    /* when we reach here, word_array is guaranteed to be the right size */
    random = rand () % max_word;
    printf ("random word #%d: %s\n", random, *(word_array + random));

抱歉，这是匆忙发布的，所以我没有测试上面的内容。买者自负。