📖

makefile

@@ -16,11 +16,11 @@ TEST := $(BASE).dtt
 
 main: ${TEST}
 	echo 'test':
-	cat ${TEST} | docker compose run advent python -u ${CODE}
+	cat ${TEST} | docker compose run --rm advent python -u ${CODE}
 
 clean: ${DATA}
 	echo 'real:'
-	cat ${DATA} | docker compose run advent python -u ${CODE}
+	cat ${DATA} | docker compose run --rm advent python -u ${CODE}
 
 ${DATA} ${TEST}:
 	# avoid spam in the lead up to the event

y2023/p10.py

@@ -0,0 +1,48 @@
+def around(x, graph, adj):
+    if x in graph:
+        for dx in adj[graph[x]]:
+            y = x + dx
+            if x in {y + dy for dy in adj[graph[y]]}:
+                yield y
+                yield x + (y - x) / 2 # this extends the pipeline to include mid-joints
+
+
+text = open(0).read()
+graph = {complex(x, y): val
+    for y, row in enumerate(text.splitlines())
+    for x, val in enumerate(row)
+}
+adj = {
+    'S': [1, -1, 1j, -1j],
+    '-': [1, -1],
+    '.': [],
+    '|': [1j, -1j],
+    'L': [1, -1j],
+    '7': [1j, -1],
+    'J': [-1j, -1],
+    'F': [1j, 1],
+}
+state = {k for k in graph if graph[k] == 'S'}
+seen = {}
+n = 0
+while state:
+    seen |= {k: n for k in state}
+    state = {y for x in state for y in around(x, graph, adj) if y not in seen}
+    n += 1
+print(max(seen.values()))
+
+
+def connected(nodes, steps):
+    while nodes:
+        edge = {nodes.pop()}
+        seen = edge.copy()
+        while edge:
+            edge = {node + step for node in edge for step in steps} & nodes - seen
+            seen |= edge
+        nodes -= seen
+        yield seen
+
+
+steps = {(dx + dy) / 2 for node in graph for dx in [-1, 0, 1] for dy in [-1j, 0, 1j]}
+nodes = {node + step for node in graph for step in steps} - set(seen)
+print(sum(len(group & set(graph)) for group in connected(nodes, steps) if not 0 in group))