Solve 2024:12 p1 "Garden Groups"

Loooong time overdue. First drafts of the code
kept track of every id separately in a defaultdict.

This was not sustainable since the code examples
had some recurring ids, and after managing to
support the test cases the code was eay off for
the real puzzle input.

In the end, the whole code was deleted and replaced
by a BFS solution that expands the current regions
until it finds no more areas.

Got the trick to count all perimiters in an else clause
from a leaderboard placed youtuber.

2024-python/output/day_12.py

@@ -0,0 +1,86 @@
+import re
+from collections import Counter, defaultdict, deque
+from heapq import heappop, heappush
+from itertools import chain, combinations, compress, permutations
+
+from output import ADJ, DD, D, ccw, cw, ints, matrix, mdbg, mhd, vdbg
+
+
+def solve(data):
+    grid, H, W = matrix(data)
+    p1 = 0
+    seen = set()
+    for r, row in enumerate(grid):
+        for c, col in enumerate(row):
+            if (r, c) in seen:
+                continue
+            areas = 0
+            perimeters = 0
+            q = deque([(r, c)])
+            while q:
+                rc = q.popleft()
+                if rc in seen:
+                    continue
+                seen.add(rc)
+                areas += 1
+                y, x = rc
+                for dy, dx in D:
+                    if (0 <= y + dy < H and 0 <= x + dx <W) and grid[y + dy][x + dx] == col:
+                        q.append((y + dy, x + dx))
+                    else:
+                        perimeters += 1
+            p1 += areas*perimeters
+    p2 = None
+    return p1, p2
+
+
+if __name__ == "__main__":
+    import os
+
+    # use dummy data
+    inp = """
+    RRRRIICCFF
+    RRRRIICCCF
+    VVRRRCCFFF
+    VVRCCCJFFF
+    VVVVCJJCFE
+    VVIVCCJJEE
+    VVIIICJJEE
+    MIIIIIJJEE
+    MIIISIJEEE
+    MMMISSJEEE
+    """.strip()
+
+    """
+    A region of R plants with price 12 * 18 = 216.
+    A region of I plants with price 4 * 8 = 32.
+    A region of C plants with price 14 * 28 = 392.
+    A region of F plants with price 10 * 18 = 180.
+    A region of V plants with price 13 * 20 = 260.
+    A region of J plants with price 11 * 20 = 220.
+    A region of C plants with price 1 * 4 = 4.
+    A region of E plants with price 13 * 18 = 234.
+    A region of I plants with price 14 * 22 = 308.
+    A region of M plants with price 5 * 12 = 60.
+    A region of S plants with price 3 * 8 = 24.
+    """
+
+    # uncomment to instead use stdin
+    # import sys; inp = sys.stdin.read().strip()
+
+    # uncomment to use AoC provided puzzle input
+    with open("./input/12.txt", "r") as f:
+        inp = f.read().strip()
+
+    # uncomment to do initial data processing shared by part 1-2
+    p1, p2 = solve(inp)
+
+    print(p1)
+    os.system(f"echo {p1} | wl-copy")
+    # print(p2)
+    # os.system(f"echo {p2} | wl-copy")
+
+    # uncomment and replace 0 with actual output to refactor code
+    # and ensure nonbreaking changes
+    assert p1 == 1446042
+    # assert p2 == 0