Solution for problem 8 part 1 in Python

src/Year_2018/P8.py

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+# --- Day 8: Memory Maneuver ---
+
+# The sleigh is much easier to pull than you'd expect for something its weight.
+# Unfortunately, neither you nor the Elves know which way the North Pole is
+# from here.
+
+# You check your wrist device for anything that might help. It seems to have
+# some kind of navigation system! Activating the navigation system produces
+# more bad news: "Failed to start navigation system. Could not read software
+# license file."
+
+# The navigation system's license file consists of a list of numbers (your
+# puzzle input). The numbers define a data structure which, when processed,
+# produces some kind of tree that can be used to calculate the license number.
+
+# The tree is made up of nodes; a single, outermost node forms the tree's root,
+# and it contains all other nodes in the tree (or contains nodes that contain
+# nodes, and so on).
+
+# Specifically, a node consists of:
+
+#     A header, which is always exactly two numbers:
+#         The quantity of child nodes.
+#         The quantity of metadata entries.
+#     Zero or more child nodes (as specified in the header).
+#     One or more metadata entries (as specified in the header).
+
+# Each child node is itself a node that has its own header, child nodes, and
+# metadata. For example:
+
+# 2 3 0 3 10 11 12 1 1 0 1 99 2 1 1 2
+# A----------------------------------
+#     B----------- C-----------
+#                      D-----
+
+# In this example, each node of the tree is also marked with an underline
+# starting with a letter for easier identification. In it, there are four
+# nodes:
+
+#     A, which has 2 child nodes (B, C) and 3 metadata entries (1, 1, 2).
+#     B, which has 0 child nodes and 3 metadata entries (10, 11, 12).
+#     C, which has 1 child node (D) and 1 metadata entry (2).
+#     D, which has 0 child nodes and 1 metadata entry (99).
+
+# The first check done on the license file is to simply add up all of the
+# metadata entries. In this example, that sum is 1+1+2+10+11+12+2+99=138.
+
+# What is the sum of all metadata entries?
+
+from typing import List
+
+with open("files/P8.txt") as f:
+    tree = [int(num) for num in f.read().strip().split()]
+
+
+def sum_metadata(lst: List[int]) -> int:
+    childs = lst.pop(0)
+    metadata = lst.pop(0)
+
+    ans = sum(sum_metadata(lst) for _ in range(childs)) + sum(
+        lst.pop(0) for _ in range(metadata)
+    )
+
+    return ans
+
+
+def part_1() -> None:
+    print(f"The sum of all metadata entries is {sum_metadata(tree)}")
+
+
+if __name__ == "__main__":
+    part_1()