[WIP] Solution to problem 6 part 1 in Python

src/Year_2019/P6.py

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+# --- Day 6: Universal Orbit Map ---
+
+# You've landed at the Universal Orbit Map facility on Mercury. Because
+# navigation in space often involves transferring between orbits, the orbit
+# maps here are useful for finding efficient routes between, for example, you
+# and Santa. You download a map of the local orbits (your puzzle input).
+
+# Except for the universal Center of Mass (COM), every object in space is in
+# orbit around exactly one other object. An orbit looks roughly like this:
+
+#                   \
+#                    \
+#                     |
+#                     |
+# AAA--> o            o <--BBB
+#                     |
+#                     |
+#                    /
+#                   /
+
+# In this diagram, the object BBB is in orbit around AAA. The path that BBB
+# takes around AAA (drawn with lines) is only partly shown. In the map data,
+# this orbital relationship is written AAA)BBB, which means "BBB is in orbit
+# around AAA".
+
+# Before you use your map data to plot a course, you need to make sure it
+# wasn't corrupted during the download. To verify maps, the Universal Orbit Map
+# facility uses orbit count checksums - the total number of direct orbits (like
+# the one shown above) and indirect orbits.
+
+# Whenever A orbits B and B orbits C, then A indirectly orbits C. This chain
+# can be any number of objects long: if A orbits B, B orbits C, and C orbits D,
+# then A indirectly orbits D.
+
+# For example, suppose you have the following map:
+
+# COM)B
+# B)C
+# C)D
+# D)E
+# E)F
+# B)G
+# G)H
+# D)I
+# E)J
+# J)K
+# K)L
+
+# Visually, the above map of orbits looks like this:
+
+#         G - H       J - K - L
+#        /           /
+# COM - B - C - D - E - F
+#                \
+#                 I
+
+# In this visual representation, when two objects are connected by a line, the
+# one on the right directly orbits the one on the left.
+
+# Here, we can count the total number of orbits as follows:
+
+#     D directly orbits C and indirectly orbits B and COM, a total of 3 orbits.
+#     L directly orbits K and indirectly orbits J, E, D, C, B, and COM, a total
+# of 7 orbits.
+#     COM orbits nothing.
+
+# The total number of direct and indirect orbits in this example is 42.
+
+# What is the total number of direct and indirect orbits in your map data?
+
+with open("files/test") as f:
+    orbits = [line for line in f.read().strip().split()]
+
+# print(orbits)
+
+from collections import defaultdict
+
+planets = defaultdict(list)
+for orbit in orbits:
+    planet, satellite = orbit.split(")")
+    planets[planet].append(satellite)
+
+
+def count_orbits(node, counter, total_sum):
+    total_sum += counter
+    for satellite in planets[node]:
+        total_sum = count_orbits(satellite, counter + 1, total_sum)
+    return total_sum
+
+
+print(count_orbits("COM", 0, 0))