c 2024 day 15 part 1

c/2024/15/warehouse_woes.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdbool.h>
+
+#include "../../lib/aoc.h"
+
+enum Direction { UP, LEFT, RIGHT, DOWN };
+
+typedef struct Position {
+  int x;
+  int y;
+} Position;
+
+typedef struct Map {
+  char *data;
+  int width;
+  int height;
+  Position robot;
+} Map;
+
+char char_at_position(Map *map, Position p) {
+  return map->data[p.x + (map->width * p.y)];
+}
+
+void set_char_at_position(Map *map, Position p, char c) {
+  map->data[p.x + (map->width * p.y)] = c;
+}
+
+bool move(Map *map, Position p, char dir) {
+  Position target;
+  switch (dir) {
+  case '^':
+    target.x = p.x;
+    target.y = p.y - 1;
+    break;
+  case '<':
+    target.x = p.x - 1;
+    target.y = p.y;
+    break;
+  case '>':
+    target.x = p.x + 1;
+    target.y = p.y;
+    break;
+  case 'v':
+    target.x = p.x;
+    target.y = p.y + 1;
+    break;
+  }
+  // printf("Moving from [%d,%d] to [%d,%d]\n", p.x, p.y, target.x, target.y);
+  bool can_move;
+  switch (char_at_position(map, target)) {
+  case '#':
+    can_move = false;
+    break;
+  case '.':
+    can_move = true;
+    break;
+  case 'O':
+    can_move = move(map, target, dir);
+    break;
+  }
+
+  if (can_move) {
+    char mover = char_at_position(map, p);
+    if (mover == '@') {
+      map->robot.x = target.x;
+      map->robot.y = target.y;
+    }
+    set_char_at_position(map, target, mover);
+    set_char_at_position(map, p, '.');
+  }
+
+  return can_move;
+}
+
+void execute_instruction(Map *m, char inst) {
+  if (inst == '\n') return;
+
+  move(m, m->robot, inst);
+}
+
+int main() {
+  char *input = aoc_read_input();
+  char *split = strstr(input, "\n\n");
+  split[1] = '\0';
+  char *instructions = split + 2;
+  int instructions_length = strlen(instructions);
+
+  int robot_index = strchr(input, '@') - input;
+
+  Map m;
+  m.data = input;
+  m.width = strchr(input, '\n') - input + 1;
+  m.height = strlen(input) / m.width;
+  m.robot.x = robot_index % m.width;
+  m.robot.y = robot_index / m.width;
+
+  for (int i = 0; i < instructions_length; i++) {
+    execute_instruction(&m, instructions[i]);
+  }
+
+  Position p;
+  int total = 0;
+  for (int i = 0; i < strlen(input); i++) {
+    p.x = i % m.width;
+    p.y = i / m.width;
+    if (char_at_position(&m, p) == 'O') total += ((100 * p.y) + p.x);
+  }
+
+  printf("Part 1: %d\n", total);
+
+  aoc_free();
+  exit(0);
+}