自己实现strncpy


//strncpy
char *strncpy(char *dst, const char *src, size_t count)
{
    assert((dst != NULL) && (src != NULL ));
    char *tmp = dst;
    tmp[count+1]='\0';
    while (count-- && (*(dst++) = *(src++))!='\0')
    {
        ;//nothing
    }
    return tmp;
    
}