Solve 2015 days 8-10.

2015/d9.py

@@ -0,0 +1,42 @@
+from lib import *
+from typing import Iterator
+
+# Just for fun instead of using itertools.permutations.
+def permutations(xs) -> Iterator:
+    assert len(xs) > 0
+    if len(xs) == 1:
+        yield xs
+    else:
+        x = xs.pop()
+        for p in permutations(xs):
+            for i in range(len(p) + 1):
+                pn = list(p)
+                pn.insert(i, x)
+                yield pn
+
+part_1 = False
+data = open(0).read()
+
+dists = {}
+nodes = set()
+for line in data.splitlines():
+    path, dist = line.split(" = ")
+    dist = int(dist)
+    a, b = path.split(" to ")
+    nodes.add(a)
+    nodes.add(b)
+    dists[(a, b)] = dist
+    dists[(b, a)] = dist
+
+if part_1:
+    mdist = 10**12
+    for route in permutations(nodes):
+        dist = sum([dists[(route[i], route[i + 1])] for i in range(len(route) - 1)])
+        mdist = min(dist, mdist)
+    print(mdist)
+else:
+    mdist = 0
+    for route in permutations(nodes):
+        dist = sum([dists[(route[i], route[i + 1])] for i in range(len(route) - 1)])
+        mdist = max(dist, mdist)
+    print(mdist)