X-Git-Url: https://git.friedersdorff.com/?a=blobdiff_plain;f=14_1.py;fp=14_1.py;h=2c6ce009d6e02a7e4f7d1b4a8ab4941acf110fdf;hb=5accd75b77aeb92f15e2a9fac235c88a8f7c86fe;hp=0000000000000000000000000000000000000000;hpb=51c5bd4e54ddb0a8a41255b58ff8ffa620db0b99;p=max%2Fadvent_of_code_2021.git

diff --git a/14_1.py b/14_1.py
new file mode 100644
index 0000000..2c6ce00
--- /dev/null
+++ b/14_1.py
@@ -0,0 +1,40 @@
+""" Pair insertion """
+import collections
+
+insertion_rules = {}
+
+with open("14_input.txt") as f:
+    polymer_template = f.readline().strip()
+    f.readline()
+
+    for line in f:
+        pair, insert = line.strip().split(" -> ")
+
+        insertion_rules[pair] = insert
+
+extended_template = []
+
+expected_length = len(polymer_template)
+
+for gen in range(10):
+    for i in range(len(polymer_template) - 1):
+
+        pair = polymer_template[i:i+2]
+        extended_template += [
+            polymer_template[i],
+            insertion_rules[pair],
+        ]
+
+    polymer_template = "".join(
+        extended_template + [polymer_template[i + 1]]
+    )
+    extended_template = []
+    expected_length += expected_length - 1
+
+    assert len(polymer_template) == expected_length, "Length unexpected"
+
+letter_count = collections.defaultdict(int)
+for letter in polymer_template:
+    letter_count[letter] += 1
+
+print(max(letter_count.values()) - min(letter_count.values()))