1 files changed, 45 insertions, 0 deletions

diff --git a/2020/day7/inside_shiny.py b/2020/day7/inside_shiny.py
new file mode 100644
index 0000000..00df40b
--- /dev/null
+++ b/2020/day7/inside_shiny.py
@@ -0,0 +1,45 @@
+import networkx as nx
+import re
+
+
+def fits_in(root):
+    """recursively count the number of bags that fit in other bags
+
+    :root: the node to count bags from
+    :returns: total
+
+    """
+    total = 1
+    for neighbour in bagtree[root]:
+        total += int(bagtree[root][neighbour]["weight"]) * fits_in(neighbour)
+    return total
+
+
+bagtree = nx.DiGraph()
+bagremover = re.compile(r" bags?\.?$")
+countandbag = re.compile(r"(\d+) (\w+ \w+)")
+
+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 a: re.sub(bagremover, "", a),
+                list(map(str.strip, child_str.split(","))),
+            )
+        )
+
+        if "no other" in children:
+            continue
+
+        for kid in children:
+            matches = re.match(countandbag, kid)
+            bagtree.add_edge(miniroot, matches.groups()[1], weight=matches.groups()[0])
+
+lengths = dict(nx.all_pairs_shortest_path(bagtree))
+
+# we don't count the shiny gold itself
+print(fits_in("shiny gold") - 1)