Day15

2024-12-15 14:26:20 +01:00
parent d10e284c22
commit 36ef1c49d0
8 changed files with 518 additions and 0 deletions
--- a/day15/c/day15.c
+++ b/day15/c/day15.c
@@ -0,0 +1,142 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAX_DIMENSION 1024
+#define MAX_MOVES 1024*1024
+
+typedef enum tile {
+    EMPTY,
+    WALL,
+    BOX,
+    ROBOT
+} tile_t;
+
+int try_move(tile_t **map, int rows, int columns, int x, int y, int dir[2]);
+
+int main() {
+    char c;
+
+    tile_t **map = calloc(MAX_DIMENSION, sizeof(map[0]));
+    int rows = 0, columns, i = 0;
+    map[0] = calloc(MAX_DIMENSION, sizeof(map[0][0]));
+
+    int reading_map = 1;
+
+    int (*moves)[2] = calloc(MAX_MOVES, sizeof(moves[0]));
+    int move_count = 0;
+
+    int robot_pos[2];
+
+    while ((c = getchar()) != EOF) {
+        if (reading_map) {
+            if (i == 0 && c == '\n') {
+                reading_map = 0;
+                continue;
+            }
+
+            switch (c) {
+                case '.':
+                    map[rows][i] = EMPTY;
+                    break;
+                case '#':
+                    map[rows][i] = WALL;
+                    break;
+                case 'O':
+                    map[rows][i] = BOX;
+                    break;
+                case '@':
+                    map[rows][i] = ROBOT;
+                    robot_pos[0] = rows;
+                    robot_pos[1] = i;
+                    break;
+            }
+
+            i++;
+            if (c != '\n') {
+                continue;
+            }
+
+            columns = i - 1;
+            i = 0;
+            rows++;
+            map[rows] = calloc(MAX_DIMENSION, sizeof(map[0][0]));
+        } else {
+            switch(c) {
+                case '>':
+                    moves[move_count][0] = 0;
+                    moves[move_count][1] = 1;
+                    move_count++;
+                    break;
+                case '<':
+                    moves[move_count][0] = 0;
+                    moves[move_count][1] = -1;
+                    move_count++;
+                    break;
+                case 'v':
+                    moves[move_count][0] = 1;
+                    moves[move_count][1] = 0;
+                    move_count++;
+                    break;
+                case '^':
+                    moves[move_count][0] = -1;
+                    moves[move_count][1] = 0;
+                    move_count++;
+                    break;
+            }
+        }
+    }
+
+    for (i = 0; i < move_count; i++) {
+        if (try_move(map, rows, columns, robot_pos[0], robot_pos[1], moves[i])) {
+            robot_pos[0] += moves[i][0];
+            robot_pos[1] += moves[i][1];
+        }
+    }
+
+    int sum = 0;
+    for (i = 0; i < rows; i++) {
+        for (int j = 0; j < columns; j++) {
+            if (map[i][j] == BOX) {
+                sum += 100 * i + j;
+            }
+        }
+    }
+
+    for (i = 0; i < rows + 1; i++) {
+        free(map[i]);
+    }
+    free(map);
+    free(moves);
+
+    printf("%i\n", sum);
+}
+
+int try_move(tile_t **map, int rows, int columns, int x, int y, int dir[2]) {
+    // Walls cannot move
+    if (map[x][y] == WALL) {
+        return 0;
+    }
+
+    // Empty space can be filled
+    if (map[x][y] == EMPTY) {
+        return 1;
+    }
+
+    // A box/robot can move if the next tile is movable
+    int next_x = x + dir[0];
+    int next_y = y + dir[1];
+    // Cannot move out of the map although it should not be possible to reach this
+    if (next_x < 0 || next_y < 0 || next_x >= rows || next_y >= columns) {
+        return 0;
+    }
+
+    int success = try_move(map, rows, columns, next_x, next_y, dir);
+
+    // If successfully moved, update map
+    if (success) {
+        map[next_x][next_y] = map[x][y];
+        map[x][y] = EMPTY;
+    }
+
+    return success;
+}