diff --git a/src/Year_2018/P8.py b/src/Year_2018/P8.py new file mode 100644 index 0000000..da9ba78 --- /dev/null +++ b/src/Year_2018/P8.py @@ -0,0 +1,72 @@ +# --- 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()