advent-of-code-2023/day_5.c

//
// Created by lennart on 12/7/23.
//

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <assert.h>
#include <ctype.h>
#include "input_handler.h"

//region types
#define LIST_NAME IntList
#define LIST_PREFIX ilist
#define ELEMENT_TYPE unsigned int
#include "list.h"

typedef struct {
    uint32_t source;
    uint32_t destination;
    uint32_t length;
} Range;

#define LIST_NAME RangeList
#define LIST_PREFIX rlist
#define ELEMENT_TYPE Range
#include "list.h"

typedef struct {
    IntList *seeds;
    RangeList *seed_to_soil;
    RangeList *soil_to_fertilizer;
    RangeList *fertilizer_to_water;
    RangeList *water_to_light;
    RangeList *light_to_temperature;
    RangeList *temperature_to_humidity;
    RangeList *humidity_to_location;
} Almanac;
//endregion types

Almanac* load_almanac(FILE *f);
RangeList* load_map(FILE *f, const char *name);
void almanac_free(Almanac *almanac);

int main() {
    FILE *f = fopen("day_5.txt", "r");
    if(f == NULL) {
        fprintf(stderr, "Missing input file!\n");
        exit(1);
    }
    Almanac *almanac = load_almanac(f);

    // Part 1 - Iterate over each seed and transform number using first matching range for each map
    uint32_t min_location = UINT32_MAX;
    for(int i = 0; i < almanac->seeds->length; i++) {
        uint32_t source = almanac->seeds->data[i];

        for(int j = 0; j < 7; j++) {
            RangeList ranges = * ((RangeList**) almanac)[j + 1];
            for(int k = 0; k < ranges.length; k++) {
                Range range = ranges.data[k];
                if(source >= range.source && source < range.source + range.length) {
                    source = source - range.source + range.destination;
                    break;
                }
            }
        }

        if(source < min_location) {
            min_location = source;
        }
    }
    printf("Result #1: %u\n", min_location);

    // Part 2
    printf("Solving part 2.\nHold your horses... this might take a while.\n");
    min_location = UINT32_MAX;
    for(int i = 0; i < almanac->seeds->length; i += 2) {
        uint32_t min = almanac->seeds->data[i];
        uint32_t icount = almanac->seeds->data[i + 1];
        for(int i2 = 0; i2 < icount; i2++) {
            uint32_t source = min + i2;
            for(int j = 0; j < 7; j++) {
                RangeList ranges = * ((RangeList**) almanac)[j + 1];
                for(int k = 0; k < ranges.length; k++) {
                    Range range = ranges.data[k];
                    if(source >= range.source && source < range.source + range.length) {
                        source = source - range.source + range.destination;
                        break;
                    }
                }
            }

            if(source < min_location) {
                min_location = source;
            }
        }
        printf(".");
    }
    printf("\nResult #2: %u\n", min_location);

    almanac_free(almanac);
    fclose(f);
    return 0;
}

Almanac* load_almanac(FILE *f) {
    Almanac *almanac = malloc(sizeof (Almanac));
    char *buffer = NULL;
    int bufferLen;

    // Load the seeds
    read_line(f, &buffer, &bufferLen);
    assert(strlen(buffer) > 7 && strncmp(buffer, "seeds: ", 7) == 0); // expect name prefix line
    almanac->seeds = ilist_create(16);
    char *cursor = &buffer[7];
    while(*cursor != 0) {
        if(!isdigit(*cursor) && cursor++) continue;
        uint32_t seed = (uint32_t) strtoul(cursor, &cursor, 10);
        ilist_add(almanac->seeds, seed);
    }
    read_line(f, &buffer, &bufferLen);
    assert(strcmp(, "") == 0); // expect empty line at end

    almanac->seed_to_soil = load_map(f, "seed-to-soil");
    almanac->soil_to_fertilizer = load_map(f, "soil-to-fertilizer");
    almanac->fertilizer_to_water = load_map(f, "fertilizer-to-water");
    almanac->water_to_light = load_map(f, "water-to-light");
    almanac->light_to_temperature = load_map(f, "light-to-temperature");
    almanac->temperature_to_humidity = load_map(f, "temperature-to-humidity");
    almanac->humidity_to_location = load_map(f, "humidity-to-location");

    free(buffer);
    return almanac;
}

RangeList* load_map(FILE *f, const char *name) {
    RangeList *list = rlist_create(16);
    char *buffer = NULL;
    int bufferLen;

    read_line(f, &buffer, &bufferLen);
    assert(strncmp(buffer, name, strlen(name)) == 0);
    while(!feof(f) && strcmp(read_line(f, &buffer, &bufferLen), "") != 0) {
        Range range;
        sscanf(buffer, "%u %u %u", &range.destination, &range.source, &range.length);
        rlist_add(list, range);
    }

    free(buffer);
    return list;
}

void almanac_free(Almanac *almanac) {
    ilist_free(almanac->seeds);
    rlist_free(almanac->seed_to_soil);
    rlist_free(almanac->soil_to_fertilizer);
    rlist_free(almanac->fertilizer_to_water);
    rlist_free(almanac->water_to_light);
    rlist_free(almanac->light_to_temperature);
    rlist_free(almanac->temperature_to_humidity);
    rlist_free(almanac->humidity_to_location);
    free(almanac);
}