aoc_omni/c/2024/18/ram_run.c

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

#include "../../lib/aoc.h"

#define DIMENSION 71
#define QUEUE_LENGTH 200

typedef struct Node {
  int x;
  int y;
  char c;
  int cost;
} Node;

typedef struct Grid {
  Node grid[DIMENSION][DIMENSION];
} Grid;

void grid_dijkstra(Grid *g) {
  Node* queue[QUEUE_LENGTH];
  queue[0] = &(g->grid[0][0]);
  int queue_start = 0;
  int queue_end = 1;

  g->grid[0][0].c = '*';
  g->grid[0][0].cost = 0;

  while (queue_start != queue_end) {
    // get first element of queue
    Node* n = queue[queue_start++];
    queue_start %= QUEUE_LENGTH;
    n->c = ' ';
    // add its neighbors to the queue
    if (n->x - 1 >= 0 && g->grid[n->x - 1][n->y].c == '.') {
      g->grid[n->x - 1][n->y].c = '*';
      g->grid[n->x - 1][n->y].cost = n->cost + 1;
      queue[queue_end++] = &(g->grid[n->x - 1][n->y]);
      queue_end %= 200;
    }

    if (n->y - 1 >= 0 && g->grid[n->x][n->y - 1].c == '.') {
      g->grid[n->x][n->y - 1].c = '*';
      g->grid[n->x][n->y - 1].cost = n->cost + 1;
      queue[queue_end++] = &(g->grid[n->x][n->y - 1]);
      queue_end %= 200;
    }

    if (n->x + 1 < DIMENSION && g->grid[n->x + 1][n->y].c == '.') {
      g->grid[n->x + 1][n->y].c = '*';
      g->grid[n->x + 1][n->y].cost = n->cost + 1;
      queue[queue_end++] = &(g->grid[n->x + 1][n->y]);
      queue_end %= 200;
    }

    if (n->y + 1 < DIMENSION && g->grid[n->x][n->y + 1].c == '.') {
      g->grid[n->x][n->y + 1].c = '*';
      g->grid[n->x][n->y + 1].cost = n->cost + 1;
      queue[queue_end++] = &(g->grid[n->x][n->y + 1]);
      queue_end %= 200;
    }
  }
}

int main() {
  char *line;
  Grid g;

  for (int i = 0; i < DIMENSION; i++) {
    for (int j = 0; j < DIMENSION; j++) {
      g.grid[i][j].x = i;
      g.grid[i][j].y = j;
      g.grid[i][j].c = '.';
      g.grid[i][j].cost = -1;
    }
  }

  int x, y;

  //while ((line = aoc_read_line()) != NULL) {
  for (int i = 0; i < 1024; i++) {
    line = aoc_read_line();
    sscanf(line, "%d,%d", &x, &y);
    g.grid[x][y].c = '#';
  }

  Grid original_grid;
  memcpy(&original_grid, &g, sizeof(Grid));

  grid_dijkstra(&g);

  printf("Part 1: %d\n", g.grid[DIMENSION - 1][DIMENSION - 1].cost);

  while ((line = aoc_read_line()) != NULL) {
    sscanf(line, "%d,%d", &x, &y);
    original_grid.grid[x][y].c = '#';
    memcpy(&g, &original_grid, sizeof(Grid));
    grid_dijkstra(&g);
    if (g.grid[DIMENSION - 1][DIMENSION - 1].cost == -1) break;
  }

  printf("Part 2: %d,%d\n", x, y);

  aoc_free();
  exit(0);
}