AdventOfCode C 2024 day 10

#include <stdio.h>
#define SIZE 100

/**
 * Plan of action: Empty barrier, val -1 arround the entire thing
 * Starting at 9, do a recursive search until point 0 is found.
 * Return the sum of how many were found
 * Woops this returns all paths, not just how many 9's can be reached
 */

void parse(FILE* file, int inputs[][SIZE], int* bounds) {
    int y = 1;
    int x = 1;
    char val;
    while ((val = fgetc(file)) != EOF) {
        if (val == '\n') {
            // End of this string of values
            y++;
            x = 1;
            continue;
        }
        inputs[y][x] = val - 48;
        x++;
    }
    y++;
    for (size_t i = 0; i < y; i++) {
        inputs[i][0] = -1;
        inputs[i][x] = -1;
    }

    x++;
    for (size_t i = 0; i < x; i++) {
        inputs[0][i] = -1;
        inputs[y][i] = -1;
    }

    bounds[0] = x;
    bounds[1] = y + 1;
}


int search_path(int locations[][SIZE], int x, int y, int prev_val) {
    int val = locations[y][x];
    if (prev_val - val != 1) {
        // Invalid
        return 0;
    }
    if (val == 0) {
        // Valid route
        return 1;
    }
    int directions[5] = { 1,0,-1,0,1 };
    int total = 0;
    for (size_t i = 0; i < 4; i++) {
        int n_x = x + directions[i];
        int n_y = y + directions[i + 1];
        total += search_path(locations, n_x, n_y, val);
    }
    return total;
}

int search_uniques(int locations[][SIZE], int found[][2], int* index, int x, int y, int prev_val) {
    int val = locations[y][x];
    if (val - prev_val != 1) {
        // Invalid
        return 0;
    }
    printf("Exploring to %d, %d\n", x, y);
    if (val == 9) {
        // Valid route
        // But check if it's already in the items
        for (size_t i = 0; i < *index; i++) {
            int dx = found[i][0];
            int dy = found[i][1];
            if (x == dx && y == dy) {
                // Not a valid route
                printf("%d, %d was already reachable\n", x, y);
                return 0;
            }
        }
        printf("%d, %d is a new reachable point\n", x, y);
        found[*index][0] = x;
        found[*index][1] = y;
        (*index)++;
        return 1;
    }
    int directions[5] = { 1,0,-1,0,1 };
    int total = 0;
    for (size_t i = 0; i < 4; i++) {
        int n_x = x + directions[i];
        int n_y = y + directions[i + 1];
        total += search_uniques(locations, found, index, n_x, n_y, val);
    }
    return total;
}

void print_map(int locations[][SIZE], int* bounds) {
    for (size_t y = 0; y < bounds[1]; y++) {
        for (size_t x = 0; x < bounds[0]; x++) {
            int loc = locations[y][x];
            printf("%c", loc + 48);

        }
        printf("\n");
    }

}

int part_one(int locations[][SIZE], int* bounds) {
    int total = 0;
    for (size_t y = 0; y < bounds[1]; y++) {
        for (size_t x = 0; x < bounds[0]; x++) {
            int loc = locations[y][x];
            if (loc == 0) {
                int found_places[SIZE][2] = { 0 };
                int index = 0;
                total += search_uniques(locations, found_places, &index, x, y, -1);
            }
        }
    }
    return total;
}
int part_two(int locations[][SIZE], int* bounds) {
    int total = 0;
    for (size_t y = 0; y < bounds[1]; y++) {
        for (size_t x = 0; x < bounds[0]; x++) {
            int loc = locations[y][x];
            if (loc == 9) {
                total += search_path(locations, x, y, 10);
            }
        }
    }
    return total;
}


int main() {
    FILE* ptr = fopen("2024-10.txt", "r");
    int bounds[2] = { 0 };
    int locations[SIZE][SIZE] = { 0 };
    parse(ptr, locations, bounds);
    print_map(locations, bounds);
    printf("Part one: %d\n", part_one(locations, bounds));
    printf("Part two: %d\n", part_two(locations, bounds));
}