From 1ffc2556d4ae91a6a568def1fb79410cf70eb795 Mon Sep 17 00:00:00 2001
From: Botond Hende <nettingman@gmail.com>
Date: Fri, 13 Dec 2024 20:52:55 +0100
Subject: 2024 day 12-13

---
 2024/day12/solve.py | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 2024/day12/solve.py

(limited to '2024/day12/solve.py')

diff --git a/2024/day12/solve.py b/2024/day12/solve.py
new file mode 100644
index 0000000..e7a6b7b
--- /dev/null
+++ b/2024/day12/solve.py
@@ -0,0 +1,92 @@
+from typing import Optional
+from functools import cmp_to_key
+
+
+def chart_region(plots: list[list[Optional[str]]], current_pos: tuple[int, int],
+                 charted_positions: list[tuple[int, int]], fence_positions: list[list[tuple[int, int]]]) -> tuple[int, int]:
+    charted_positions.append(current_pos)
+    current_plot = plots[current_pos[0]][current_pos[1]]
+
+    plot_count = 1
+    fence_count = 0
+
+    row_cnt = len(data)
+    col_cnt = len(data[0])
+    for dir_idx, direct in enumerate(((-1, 0), (1, 0), (0, -1), (0, 1))):
+        new_pos = (current_pos[0] + direct[0], current_pos[1] + direct[1])
+        if 0 <= new_pos[0] < row_cnt and 0 <= new_pos[1] < col_cnt and plots[new_pos[0]][new_pos[1]] == current_plot:
+            if new_pos not in charted_positions:
+                result = chart_region(plots, new_pos, charted_positions, fence_positions)
+                plot_count += result[0]
+                fence_count += result[1]
+        else:
+            fence_positions[dir_idx].append(current_pos)
+            fence_count += 1
+
+    return plot_count, fence_count
+
+
+def compare_row_first(item1: tuple[int, int], item2: tuple[int, int]):
+    row_diff = item1[0] - item2[0]
+    if row_diff != 0:
+        return row_diff
+
+    return item1[1] - item2[1]
+
+
+def compare_col_first(item1: tuple[int, int], item2: tuple[int, int]):
+    col_diff = item1[1] - item2[1]
+    if col_diff != 0:
+        return col_diff
+
+    return item1[0] - item2[0]
+
+
+def calculate_discount(fence_positions: list[list[tuple[int, int]]]) -> int:
+    adjacents = 0
+    for charted_positions in fence_positions:
+        charted_positions.sort(key=cmp_to_key(compare_row_first))
+        last_pos = None
+        for current_pos in charted_positions:
+            if last_pos is not None and last_pos[0] == current_pos[0] and last_pos[1] + 1 == current_pos[1]:
+                adjacents += 1
+
+            last_pos = current_pos
+
+        charted_positions.sort(key=cmp_to_key(compare_col_first))
+        last_pos = None
+        for current_pos in charted_positions:
+            if last_pos is not None and last_pos[1] == current_pos[1] and last_pos[0] + 1 == current_pos[0]:
+                adjacents += 1
+
+            last_pos = current_pos
+
+    return adjacents
+
+
+use_discount = True  # for part two
+
+data = []
+with open("input") as f:
+    for line in f:
+        data.append(list(line.strip()))
+
+row_count = len(data)
+col_count = len(data[0])
+
+final_sum = 0
+
+for row in range(row_count):
+    for col in range(col_count):
+        if data[row][col] is not None:
+            charted_pos: list[tuple[int, int]] = []
+            fence_pos: list[list[tuple[int, int]]] = [[], [], [], []]
+            chart_result = chart_region(data, (row, col), charted_pos, fence_pos)
+            fences = chart_result[1]
+            if use_discount:
+                fences -= calculate_discount(fence_pos)
+            final_sum += chart_result[0] * fences
+            for pos in charted_pos:
+                data[pos[0]][pos[1]] = None
+
+print(final_sum)
-- 
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