char * dedupe(char * str) {
    if(str == nullptr || strlen(str) == 0) return str;
    char * ptr = str;
    char * pos = str;
    while(*ptr) {
        *pos = *ptr;
        while(*ptr && *pos == *++ptr);
        ptr--;
        *pos++ = *ptr++;
    }
    *pos++ = '\0';
    return str;
}