实现统计一个字符串所含的不同字符的总数

#include <stdio.h>

int charCount(char *str)
{
    int iCount = 0;
    int i, j, k=0;
    char *p = str;
    char *q = p;
    while (*p)
    {
        p++;
        k++;
    }
    for (i=0; i<128; i++)
    {
        str = q;
        for (j=0; j<k; j++)
        {
            if (i == *str)
            {
                iCount++;
                break;
            }
            str++;
        }
    }
    return iCount;
}

int main()
{
    char *p = "   abcdeef121";
    printf("%d\n", charCount(p));
    return 0;
}