c - Boyer-Moore-Horspool 实现

Question

我想获得 Boyer-Moore-Horspool 实现来搜索文本文件中的某些字符串。这是我的代码:

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

int bmhSearch(char *needle) {
    FILE *fp;
    int find_result = 0;
    char temp[512];

    size_t nlen = strlen(needle);

    size_t scan = 0;
    size_t bad_char_skip[UCHAR_MAX + 1];
    size_t last;

    if((fopen_s(&fp, "book.txt", "r")) != NULL) {
        return(-1);
    }

    while(fgets(temp, 512, fp) != NULL) {
        size_t hlen = strlen(temp);
        /* pre */
        for (scan = 0; scan <= UCHAR_MAX; scan = scan + 1)
            bad_char_skip[scan] = nlen;
        last = nlen - 1;
        for (scan = 0; scan < last; scan = scan + 1)
            bad_char_skip[needle[scan]] = last - scan;

        while (hlen >= nlen){
            /* scan from the end of the needle */
            char *ptemp = temp;
            for (scan = last; ptemp[scan] == needle[scan]; scan = scan - 1){
                if (scan == 0){
                    find_result++;
                }
            }

            hlen     -= bad_char_skip[ptemp[last]];
            ptemp += bad_char_skip[ptemp[last]];
            printf("%d\t%d\n", hlen, nlen);
        }
    }

    if(fp) {
        fclose(fp);
    }
    return find_result;
}

int main(void){
    char needle[30] = {"some text like this"};
    printf("Matches found: %d\n", bmhSearch(needle);
}

我相信，我做错了很多事情，但我真的找不到并修复它。我唯一得到的是程序在某个阶段不符合条件 while(hlen >= nlen)。

Answer 1

如果问题是“代码有什么问题？”；这里有一些事情可以开始:

 printf("Matches found: %d\n", bmhSearch(needle); // Missing a final ')'.

---

 int main(void)
    {
    ...
    return(0);  // Something like this line is required for a function that returns'int'.
    } 

---

     size_t bad_char_skip[UCHAR_MAX + 1];  // Requires: '#include <limits.h>

---

     if((fopen_s(&fp, "book.txt", "r")) != NULL) {

函数“fopen_s()”不返回指针。它返回一个 errno_t 类型，它是一个整数值。将整数与“NULL”进行比较就像打扮成牛仔出现在“印度战舞”中一样。也许以下更合适:

     if((fopen_s(&fp, "book.txt", "r")) != 0) {

相当于(我最喜欢的):

     if(fopen_s(&fp, "book.txt", "r")) {

---

        printf("%d\t%d\n", hlen, nlen);

上面的格式字符串不正确。应该是:

        printf("%zu\t%zu\n", hlen, nlen);

---

在严格的 C 意义上，需要注意以下几行:

        bad_char_skip[needle[scan]] = last - scan;

        hlen  -= bad_char_skip[ptemp[last]];
        ptemp += bad_char_skip[ptemp[last]];

它们应更改为以下内容:

        bad_char_skip[(int)needle[scan]] = last - scan;

        hlen  -= bad_char_skip[(int)ptemp[last]];
        ptemp += bad_char_skip[(int)ptemp[last]];

变量“ptemp”被定义为“char *”。因此; 'ptemp[n]' 评估为 'char' 类型；而数组索引号必须是“int”。