#include <stdio.h>
#include <stdlib.h>
#include <string.h>

struct ascii_set {
    unsigned long long lo;
    unsigned long long hi;
};

bool ascii_set_insert(struct ascii_set *set, char ch)
{
    unsigned long long mask = 1ULL << (ch % 64);

    if (ch < 64) {
        if (set->lo & mask) {
            set->lo = mask;
            set->hi = 0;
            return false;
        } else {
            set->lo |= mask;
            return true;
        }
    } else {
        if (set->hi & mask) {
            set->hi = mask;
            set->lo = 0;
            return false;
        } else {
            set->hi |= mask;
            return true;
        }
    }
}

unsigned longest_no_repeat(char *str, unsigned len)
{
    struct ascii_set set = {0};

    unsigned longest = 0;
    unsigned current = 0;

    for (unsigned i = 0; i < len; i++) {
        if (ascii_set_insert(&set, str[i])) {
            current++;
        } else {
            if (current > longest)
                longest = current;
            
            current = 1;
        }
    }

    if (current > longest)
        longest = current;

    return longest;
}

int main()
{
    char buf[2048];

    while (true) {
        fputs("enter a string nya: ", stdout);
        fgets(buf, 2048, stdin);
        unsigned len = strlen(buf);
        buf[--len] = '\0';

        unsigned longest = longest_no_repeat(buf, len);
        printf("longest without repeating is %u nya\n", longest);
    }

    return 0;
}