程序代码：

int longest(char string[])
{
    int i, flag = 1, len = 0, length = 0, place = 0, point = 0;
    for (i = 0; i <= strlen(string); i++)
        if (alphbetic(string[i]))
            if (flag)
            {
                point = i;
                flag = 0;
            }
            else
                len++;
        else
        {
            flag = 1;
            if (len >= length)
            {
                length = len;
                place = point;
            }
            len = 0;
        }
    return(place);
}