1 files changed, 35 insertions, 0 deletions

diff --git a/2020/day7/haversacks.py b/2020/day7/haversacks.py
new file mode 100644
index 0000000..4f7292d
--- /dev/null
+++ b/2020/day7/haversacks.py
@@ -0,0 +1,35 @@
+import networkx as nx
+import re
+
+bagtree = nx.DiGraph()
+bagremover = re.compile(r" bags?\.?$")
+numremover = re.compile(r"^\d+ ")
+
+with open("input", "r") as baglines:
+    for line in baglines:
+        (miniroot, child_str) = list(map(str.strip, line.split("contain")))
+
+        miniroot = miniroot.replace(" bags", "")
+
+        children = list(
+            map(
+                lambda b: re.sub(numremover, "", b),
+                list(
+                    map(
+                        lambda a: re.sub(bagremover, "", a),
+                        list(map(str.strip, child_str.split(","))),
+                    )
+                ),
+            )
+        )
+
+        if "no other" in children:
+            continue
+
+        for kid in children:
+            bagtree.add_edge(kid, miniroot)
+
+lengths = dict(nx.all_pairs_shortest_path(bagtree))
+
+# we don't count the shiny gold itself
+print(len(lengths["shiny gold"]) - 1)