day 25, part 1

day-25/main.c

@@ -0,0 +1,83 @@
+#include "aoc.h"
+
+typedef struct Pattern {
+    i8 heights[5];
+} Pattern;
+
+typedef DYNAMIC_ARRAY(Pattern) Patterns;
+
+static Pattern
+parse_lock_or_key(Grid grid, bool *is_lock) {
+    *is_lock = true;
+    for (isize x = 0; x < grid.width; x++) {
+        if (grid.grid[x] != '#') {
+            *is_lock = false;
+            break;
+        }
+    }
+
+    Pattern result = {0};
+    ASSERT(grid.width == ARRAY_SIZE(result.heights));
+    for (isize x = 0; x < grid.width; x++) {
+        i8 height = 0;
+        if (*is_lock) {
+            for (isize y = 0; y < grid.height && grid.grid[y * grid.width + x] == '#'; y++) {
+                height++;
+            }
+        }
+        else {
+            for (isize y = grid.height - 1; y >= 0 && grid.grid[y * grid.width + x] == '#'; y--) {
+                height++;
+            }
+        }
+        result.heights[x] = height - 1;
+    }
+    /* printf("Result: %d %d %d %d %d\n", result.heights[0], result.heights[1], result.heights[2], result.heights[3], result.heights[4]); */
+    return result;
+}
+
+static bool
+fits(Pattern lock, Pattern key) {
+    for (isize x = 0; x < ARRAY_SIZE(lock.heights); x++) {
+        if (lock.heights[x] + key.heights[x] > 5) {
+            return false;
+        }
+    }
+    return true;
+}
+
+int main(int argc, char **argv) {
+    Arena *arena = make_arena(Megabytes(1));
+    Arena *temp = make_arena(Megabytes(1));
+    str input = read_file(arena, argv[1]);
+
+    Patterns locks = {0};
+    Patterns keys = {0};
+
+    str entry;
+    while ((entry = str_next_token(&input, STR("\n\n"))).len > 0) {
+        Grid grid = parse_grid(entry, temp);
+        bool is_lock;
+        Pattern pattern = parse_lock_or_key(grid, &is_lock);
+        if (is_lock) {
+            *push(&locks, arena) = pattern;
+        }
+        else {
+            *push(&keys, arena) = pattern;
+        }
+        arena_clear(temp);
+    }
+
+    i32 part_1 = 0;
+    for (isize lock_index = 0; lock_index < locks.len; lock_index++) {
+        Pattern lock = locks.data[lock_index];
+        for (isize key_index = 0; key_index < keys.len; key_index++) {
+            Pattern key = keys.data[key_index];
+            if (fits(lock, key)) {
+                part_1++;
+                /* printf("Lock %ld fits key %ld\n", lock_index, key_index); */
+            }
+        }
+    }
+    printf("%d\n", part_1);
+}

day-25/test.txt

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+#####
+.####
+.####
+.####
+.#.#.
+.#...
+.....
+
+#####
+##.##
+.#.##
+...##
+...#.
+...#.
+.....
+
+.....
+#....
+#....
+#...#
+#.#.#
+#.###
+#####
+
+.....
+.....
+#.#..
+###..
+###.#
+###.#
+#####
+
+.....
+.....
+.....
+#....
+#.#..
+#.#.#
+#####