程序代码：

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

int countType(const char *s) /* FIXME 只支持ASCII */
{
    char *buffer = calloc(sizeof (char), strlen(s)+1);
    int bufferNo = 0;
    memset(buffer, '\0', sizeof (char) * (strlen(s)+1));

    for (; *s; ++s)
    {
        if (NULL == strchr(buffer, *s))
        {
            buffer[bufferNo++] = *s;
        }
    }

    free(buffer);
    return bufferNo;
}

int main(int argc, char *argv[])
{
    char s[] = "abcdefaa,./12456";
    printf("%s %d\n", s, countType(s));

    return 0;
}