adventofcode2024/day21/c/day21.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <limits.h>

#define CODE_LEN 4
#define CODES 5
#define CODE_MAX_LEN 16*1024
#define sgn(a) ((a) < 0 ? -1 : ((a) > 0 ? 1 : 0))
#define min(a,b) ((a) < (b) ? (a) : (b))
#define abs(a) ((a) < 0 ? -(a) : (a))

typedef enum {
    NUMERIC,
    DIRECTIONAL
} panel_type;

typedef struct node {
    struct node *children[11];
    uint64_t value;
    uint64_t value2;
    char key;
    uint8_t is_leaf;
} node_t;


typedef struct layer {
    panel_type type;
    struct layer *next_layer;
    int current_position[2];
    int id;
    node_t *trie;
} layer_t;

const int numeric_panel[][2] = {
    {3, 1}, // 0
    {2, 0}, // 1
    {2, 1}, // 2
    {2, 2}, // 3
    {1, 0}, // 4
    {1, 1}, // 5
    {1, 2}, // 6
    {0, 0}, // 7
    {0, 1}, // 8
    {0, 2}, // 9
    {3, 2}, // A
};

const int directional_panel[][2] = {
    {0, 1}, // UP
    {1, 0}, // LEFT
    {1, 1}, // DOWN
    {1, 2}, // RIGHT
    {0, 2}, // A
};

#define UP 0
#define LEFT 1
#define DOWN 2
#define RIGHT 3

#define d2c(a) ((a) == UP ? '^' : ((a) == LEFT ? '<' : ((a) == DOWN ? 'v' : ((a) == RIGHT ? '>' : 'A'))))

layer_t* create_numeric_layer() {
    layer_t *layer = calloc(1, sizeof(layer[0]));
    layer->type = NUMERIC;
    layer->next_layer = NULL;
    layer->current_position[0] = numeric_panel[10][0];
    layer->current_position[1] = numeric_panel[10][1];
    layer->trie = calloc(1, sizeof(node_t));
    return layer;
}

layer_t* create_directional_layer() {
    layer_t *layer = calloc(1, sizeof(layer[0]));
    layer->type = DIRECTIONAL;
    layer->next_layer = NULL;
    layer->current_position[0] = directional_panel[4][0];
    layer->current_position[1] = directional_panel[4][1];
    layer->trie = calloc(1, sizeof(node_t));
    return layer;
}

int c2n(char code) {
    if (code == 'A') {
        return 10;
    }

    return code - 48;
}

node_t* create_node() {
    node_t *node = calloc(1, sizeof(node[0]));
    return node;
}

node_t* search(node_t* root, int* word, int len) {
    node_t* node = root;
    for (int i = 0; i < len; i++) {
        if (node->children[word[i]] == NULL) {
            return NULL;
        }
        node = node->children[word[i]];
    }
    return node;
}

void insert(node_t* root, int* word, int len, uint64_t value, int value2) {
    node_t* node = root;
    for (int i = 0; i < len; i++) {
        if (node->children[word[i]] == NULL) {
            node->children[word[i]] = create_node();
        }
        node = node->children[word[i]];
    }
    node->value = value;
    node->value2 = value2;
    node->is_leaf = 1;
}

void free_node(node_t* node) {
    for (int i = 0; i < 11; i++) {
        if (node->children[i] != NULL) {
            free_node(node->children[i]);
        }
    }

    free(node);
}

uint64_t process_layer(layer_t *layer, int *code, uint64_t code_len, int *new_code, uint64_t new_code_len);
uint64_t process_layer2(layer_t *layer, int* code, uint64_t code_len);
int coords_to_idx(layer_t *layer, int coords[2]);
uint64_t cost_of_activation(layer_t *layer, int button);

int main() {
    char c;

    char codes[CODES][CODE_LEN];
    int code_count = 0, character_count = 0;

    while ((c = getchar()) != EOF) {
        codes[code_count][character_count++] = c;
        if (c != '\n') {
            continue;
        }
        character_count = 0;
        code_count++;
    }

    // Create Layers
    layer_t **layers = calloc(26, sizeof(layer_t*));
    // First is the numeric panel
    layers[0] = create_numeric_layer();
    layers[0]->id = 0;
    // Create directional layers
    for (int i = 1; i < 26; i++) {
        layers[i] = create_directional_layer();
        layers[i]->id = i;
    }
    // Link layers
    for (int i = 0; i < 25; i++) {
        layers[i]->next_layer = layers[i+1];
    }

    uint64_t sum = 0;
    for (int i = 0; i < code_count; i++) {
        // Convert code chars to int
        int code_encoded[4];
        for (int j = 0; j < 4; j++) {
            code_encoded[j] = c2n(codes[i][j]);
        }

        int *ccode = calloc(CODE_MAX_LEN, sizeof(ccode[0]));
        //uint64_t a = process_layer(layers[0], code_encoded, 4, ccode, 0);
        int code_encoded2[5];
        for (int j = 0; j < 4; j++) {
            code_encoded2[j+1] = c2n(codes[i][j]);
        }
        code_encoded2[0] = 10;
        uint64_t a = process_layer2(layers[0], code_encoded2, 5);
        free(ccode);
        int b;
        sscanf(codes[i], "%d", &b);
        sum += a * (uint64_t)b;
    }
    printf("%lu\n", sum);

    for (int i = 0; i < 26; i++) {
        free_node(layers[i]->trie);
        free(layers[i]);
    }
    free(layers);
}

uint64_t process_layer(layer_t *layer, int *code, uint64_t code_len, int *new_code, uint64_t new_code_len) {
    if (code_len == 0) {
        if (layer->next_layer == NULL) {
            return new_code_len;
        }
        int *ccode = calloc(CODE_MAX_LEN, sizeof(ccode[0]));
        uint64_t result = process_layer(layer->next_layer, new_code, new_code_len, ccode, 0);
        free(ccode);
        return result;
    }

    int current_position[2];
    current_position[0] = layer->current_position[0];
    current_position[1] = layer->current_position[1];

    int (*panel)[2] = layer->type == NUMERIC ? numeric_panel : directional_panel;
    // Check if we are on the right button
    if (current_position[0] == panel[code[0]][0] && current_position[1] == panel[code[0]][1]) {
        // Click button
        new_code[new_code_len] = 4;
        return process_layer(layer, code + 1, code_len - 1, new_code, new_code_len+1);
    }

    uint64_t ncl = new_code_len;
    uint64_t value1 = UINT64_MAX, value2 = UINT64_MAX;
    // Try going in each direction towards the next button
    if (current_position[0] != panel[code[0]][0]) {
        // Up or down
        if (current_position[0] - panel[code[0]][0] > 0) {
            for (int i = 0; i < current_position[0] - panel[code[0]][0]; i++) {
                new_code[new_code_len++] = UP;
            }
        } else {
            for (int i = 0; i < panel[code[0]][0] - current_position[0]; i++) {
                new_code[new_code_len++] = DOWN;
            }
        }
        layer->current_position[0] = panel[code[0]][0];
        // Cannot go to empty space
        if ((layer->type == NUMERIC && layer->current_position[0] == 3 && layer->current_position[1] == 0) || (layer->type == DIRECTIONAL && layer->current_position[0] == 0 && layer->current_position[1] == 0)) {
        } else {
            value1 = process_layer(layer, code, code_len, new_code, new_code_len);
        }
    }
    layer->current_position[0] = current_position[0];
    layer->current_position[1] = current_position[1];
    new_code_len = ncl;

    if (current_position[1] != panel[code[0]][1]) {
        // Up or down
        if (current_position[1] - panel[code[0]][1] > 0) {
            for (int i = 0; i < current_position[1] - panel[code[0]][1]; i++) {
                new_code[new_code_len++] = LEFT;
            }
        } else {
            for (int i = 0; i < panel[code[0]][1] - current_position[1]; i++) {
                new_code[new_code_len++] = RIGHT;
            }
        }
        layer->current_position[1] = panel[code[0]][1];
        // Cannot go to empty space
        if ((layer->type == NUMERIC && layer->current_position[0] == 3 && layer->current_position[1] == 0) || (layer->type == DIRECTIONAL && layer->current_position[0] == 0 && layer->current_position[1] == 0)) {
        } else {
            value2 = process_layer(layer, code, code_len, new_code, new_code_len);
        }
    }
    layer->current_position[0] = current_position[0];
    layer->current_position[1] = current_position[1];


    uint64_t value = min(value1, value2);

    return value;
}

uint64_t process_layer2(layer_t *layer, int* code, uint64_t code_len) {
    uint64_t sum = 0;
    if (layer == NULL) {
        return 1;
    }
    int (*panel)[2] = layer->type == NUMERIC ? numeric_panel : directional_panel;
    int current_position[2];
    int button_count = layer->type == NUMERIC ? 11 : 5;

    // Build cache for each combination
    if (layer->trie->children[0] == NULL) {
        for (int i = 0; i < button_count; i++) {
            for (int j = 0; j < button_count; j++) {
                int combination[2] = {i, j};
                int start1[2] = {panel[i][0], panel[i][1]};
                int start2[2] = {panel[i][0], panel[i][1]};
                int end[2] = {panel[j][0], panel[j][1]};

                int last_action1 = 4;
                // X first, Y second
                uint64_t distance1 = 0;
                while (start1[0] != end[0]) {
                    int dir = sgn(end[0] - start1[0]);
                    start1[0] += dir;
                    if ((layer->type == NUMERIC && start1[0] == 3 && start1[1] == 0) || (layer->type == DIRECTIONAL && start1[0] == 0 && start1[1] == 0)) {
                        distance1 = UINT64_MAX;
                        break;
                    }
                    int subcombination[2];
                    subcombination[0] = last_action1;
                    if (dir == -1) {
                        subcombination[1] = UP;
                        last_action1 = UP;
                    } else {
                        subcombination[1] = DOWN;
                        last_action1 = DOWN;
                    }
                    distance1 += process_layer2(layer->next_layer, subcombination, 2);
                }
                if (distance1 != UINT64_MAX) {
                    while (start1[1] != end[1]) {
                        int dir = sgn(end[1] - start1[1]);
                        start1[1] += dir;
                        int subcombination[2];
                        subcombination[0] = last_action1;
                        if (dir == -1) {
                            subcombination[1] = LEFT;
                            last_action1 = LEFT;
                        } else {
                            subcombination[1] = RIGHT;
                            last_action1 = RIGHT;
                        }
                        distance1 += process_layer2(layer->next_layer, subcombination, 2);
                    }
                }
                if (distance1 != UINT64_MAX) {
                    int activatecombination[2] = {last_action1, 4};
                    distance1 += process_layer2(layer->next_layer, activatecombination, 2);
                }

                int last_action2 = 4;
                // Y first, X second
                uint64_t distance2 = 0;
                while (start2[1] != end[1]) {
                    int dir = sgn(end[1] - start2[1]);
                    start2[1] += dir;
                    if ((layer->type == NUMERIC && start2[0] == 3 && start2[1] == 0) || (layer->type == DIRECTIONAL && start2[0] == 0 && start2[1] == 0)) {
                        distance2 = UINT64_MAX;
                        break;
                    }
                    int subcombination[2];
                    subcombination[0] = last_action2;
                    if (dir == -1) {
                        subcombination[1] = LEFT;
                        last_action2 = LEFT;
                    } else {
                        subcombination[1] = RIGHT;
                        last_action2 = RIGHT;
                    }
                    distance2 += process_layer2(layer->next_layer, subcombination, 2);
                }
                if (distance2 != UINT64_MAX) {
                    while (start2[0] != end[0]) {
                        int dir = sgn(end[0] - start2[0]);
                        start2[0] += dir;
                        int subcombination[2];
                        subcombination[0] = last_action2;
                        if (dir == -1) {
                            subcombination[1] = UP;
                            last_action2 = UP;
                        } else {
                            subcombination[1] = DOWN;
                            last_action2 = DOWN;
                        }
                        distance2 += process_layer2(layer->next_layer, subcombination, 2);
                    }
                }
                if (distance2 != UINT64_MAX) {
                    int activatecombination[2] = {last_action2, 4};
                    distance2 += process_layer2(layer->next_layer, activatecombination, 2);
                }

                uint64_t distance = distance1;
                int last_action = last_action1;
                if (distance1 > distance2) {
                    distance = distance2;
                    last_action = last_action2;
                }

                //printf("Layer %i: cost from %i to %i is %lu\n", layer->id, i, j, distance);
                insert(layer->trie, combination, 2, distance, last_action);
            }
        }
    }

    for (uint64_t i = 1; i < code_len; i++) {
        int combination[2] = {code[i-1], code[i]};
        node_t *node = search(layer->trie, combination, 2);
        sum += node->value;
    }

    return sum;
}

int coords_to_idx(layer_t *layer, int coords[2]) {
    int idx;
    int (*panel)[2] = layer->type == NUMERIC ? numeric_panel : directional_panel;
    for (idx = 0; idx < (layer->type == NUMERIC ? 11 : 5); idx++) {
        if (coords[0] == panel[idx][0] && coords[1] == panel[idx][1]) {
            break;
        }
    }

    return idx;
}

uint64_t cost_of_activation(layer_t *layer, int button) {
    if (layer == NULL) {
        return 1;
    }

    // Build cache if not present
    if (layer->trie->children[0] == NULL) {
        process_layer2(layer, NULL, 0);
    }

    int combination[2] = {button, 4};
    node_t *node = search(layer->trie, combination, 2);

    return node->value + cost_of_activation(layer->next_layer, node->value2);
}