c - 将精确的字符串与 strstr 匹配

Question

假设我有以下字符串:

in the interior of the inside is an inner inn

我想搜索“in”的出现次数(“in”出现的频率)。

在我的程序中，我使用了 strstr 来这样做，但它返回了误报。它将返回:

- in the interior of the inside is an inner inn
- interior of the inside is an inner inn
- inside is an inner inn
- inner inn
- inn

这样认为“in”出现了5次，显然是不正确的。

我应该如何进行才能专门搜索“in”这个词？

Answer 1

尝试以下操作

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

int main(void) 
{
    char *s = "in the interior of the inside is an inner inn";
    char *t = "in";
    size_t n = strlen( t );

    size_t count = 0;
    char *p = s;

    while ( ( p = strstr( p, t ) ) != NULL )
    {
        char *q = p + n;
        if ( p == s || isblank( ( unsigned char ) *( p - 1 ) ) )
        {
            if ( *q == '\0' || isblank( ( unsigned char ) *q ) ) ++count;
        }
        p = q;
    }

    printf( "There are %zu string \"%s\"\n", count, t );

    return 0;
}

输出是

There are 1 string "in"

如果源字符串可以包含标点符号，您还可以添加对 ispunct 的检查。