C 标准库 strcspn 函数的实现

/* * strcspn 在str1中查找str2中的关键字 */#include <cstdio>size_t strcspn ( const char * str1, const char * str2 ) {    char *p1 = (char *)str1;    char *p2;    while (*p1 != '\0') {        p2 = (char *)str2;        while (*p2 != '\0') {            if (*p2 == *p1) return p1-str1;            ++p2;        }        ++p1;    }    return  p1 - str1;}int main (){    char str[] = "fcba73";    char keys[] = "1234567890";    int i;    i = strcspn (str,keys);    printf ("The first number in str is at position %d.\n",i+1);    return 0;}