AoC 2024 day 22

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

#define filename    "input_22_1.txt"

#define HLEN    64321

typedef struct {
    uint32_t diffcombo[2000];   // each diffcombo consist of 4 int8_t-s in exact order, which creates a 32-bit code.
    int8_t   last[2000];
} data_t;

typedef struct {
    uint32_t addr;
    bool     pending;
    int8_t   pendingvalue;
    int32_t  value;
} object_t;

data_t   data;//[1550];
object_t hashmap[HLEN];

uint64_t calcSecret(uint64_t secret)
{
    uint64_t new;
    new = secret * 64;
    secret = new ^ secret;     //mix
    new = secret % 16777216;   //prune
    new = new / 32;
    secret = new ^ secret;     //mix
    new = secret % 16777216;   //prune
    new = new * 2048;
    secret = new ^ secret;     //mix
    new = secret % 16777216;   //prune
    return new;
}

void addLastNrIntoMap(uint32_t address, int8_t value)
{
    uint16_t index = address % HLEN;
    do {
        if ((hashmap[index].addr == 0) || (hashmap[index].addr == address)) {
            hashmap[index].addr = address;
            if (!hashmap[index].pending) {
                hashmap[index].pending = true;
                hashmap[index].pendingvalue = value;
            }
            return;
        }
        index++;
        index %= HLEN;
    } while (1);
}

void transferPendingValues(void)
{
    for (int i=0;i<HLEN;i++) {
        hashmap[i].value += hashmap[i].pendingvalue;
        hashmap[i].pending = false;
    };
}

uint64_t calc2000th(uint64_t secret, data_t * dptr)
{
    uint64_t new = secret;
    int i =0;
    dptr->last[0] = (int8_t)(-100);
    dptr->diffcombo[0] = 0;
    do {
        new = calcSecret(new);
        i++;
        dptr->last[i] = (int8_t)(new % 10);
        dptr->diffcombo[i] = (dptr->diffcombo[i-1] << 8) + (uint8_t)(dptr->last[i] - dptr->last[i-1]);
        if (i>3)
            addLastNrIntoMap(dptr->diffcombo[i], dptr->last[i]);
    } while (i<2000);
    transferPendingValues();
    return new;
}

int main()
{
    FILE * f;
    uint64_t result1 = 0;
    int num;
    int i=0;
    f = fopen(filename, "r");
    if (f != NULL) {
        char line[160] = {0};
        while (!feof(f)) {
            if ((NULL != fgets(line, sizeof(line), f)) && (strlen(line) > 1)) {
                num = atoi(line);
                result1 += calc2000th(num, &data/*[i]*/);
                i++;
            }
        }
        fclose(f);
    }
    printf("Result 1 (%i numbers): %lld\n\r", i, result1);

    int max=0;
    uint32_t maxdiff=0;
    for (int h=0;h<HLEN;h++) {
        if ((hashmap[h].addr != 0) && (hashmap[h].value > max)) {
            max = hashmap[h].value;
            maxdiff = hashmap[h].addr;
        }
    }
    printf("Result 2: %i\n\r", max);
    printf("          (%i,%i,%i,%i)\n\r", (int8_t)(maxdiff>>24), (int8_t)(maxdiff>>16), (int8_t)(maxdiff>>8), (int8_t)(maxdiff>>0));
    return 0;
}