Add day09, 2025

Author: snhansen

2025/day09/solution.py

@@ -0,0 +1,30 @@
+from itertools import combinations
+from shapely.geometry.polygon import Polygon, LineString
+
+with open("input") as f:
+    inp = f.read().strip().split("\n")
+
+coords = [(x, y) for x, y in (map(int, line.split(",")) for line in inp)]
+
+# Part 1
+print(
+    max(
+        (abs(x1 - x2) + 1) * (abs(y1 - y2) + 1)
+        for (x1, y1), (x2, y2) in combinations(coords, 2)
+    )
+)
+
+# Part 2
+polygon = Polygon(coords)
+ans = 0
+
+for (x1, y1), (x2, y2) in combinations(coords, 2):
+    p1 = (x1, y1)
+    p2 = (x2, y2)
+    p3 = (x1, y2)
+    p4 = (x2, y1)
+    lines = [LineString([p1, p3]), LineString([p1, p4]), LineString([p3, p2]), LineString([p2, p4])]
+    if all(line.covered_by(polygon) for line in lines):
+        ans = max(ans, (abs(x1 - x2) + 1)*(abs(y1 - y2) + 1))
+
+print(ans)