aoc-2019-c

Advent of Code 2019 Solutions in C
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part1 (2242B)

      1--- Day 6: Universal Orbit Map ---
      2
      3You've landed at the Universal Orbit Map facility on Mercury.  Because navigation in space often
      4involves transferring between orbits, the orbit maps here are useful for finding efficient routes
      5between, for example, you and Santa. You download a map of the local orbits (your puzzle input).
      6
      7Except for the universal Center of Mass (COM), every object in space is in orbit around exactly one
      8other object.  An orbit looks roughly like this:
      9
     10                  \
     11                   \
     12                    |
     13                    |
     14AAA--> o            o <--BBB
     15                    |
     16                    |
     17                   /
     18                  /
     19
     20In this diagram, the object BBB is in orbit around AAA. The path that BBB takes around AAA (drawn
     21with lines) is only partly shown. In the map data, this orbital relationship is written AAA)BBB,
     22which means "BBB is in orbit around AAA".
     23
     24Before you use your map data to plot a course, you need to make sure it wasn't corrupted during the
     25download.  To verify maps, the Universal Orbit Map facility uses orbit count checksums - the total
     26number of direct orbits (like the one shown above) and indirect orbits.
     27
     28Whenever A orbits B and B orbits C, then A indirectly orbits C.  This chain can be any number of
     29objects long: if A orbits B, B orbits C, and C orbits D, then A indirectly orbits D.
     30For example, suppose you have the following map:
     31
     32COM)B
     33B)C
     34C)D
     35D)E
     36E)F
     37B)G
     38G)H
     39D)I
     40E)J
     41J)K
     42K)L
     43
     44Visually, the above map of orbits looks like this:
     45
     46        G - H       J - K - L
     47       /           /
     48COM - B - C - D - E - F
     49               \
     50                I
     51
     52In this visual representation, when two objects are connected by a line, the one on the right
     53directly orbits the one on the left.
     54
     55Here, we can count the total number of orbits as follows:
     56
     57
     58 - D directly orbits C and indirectly orbits B and COM, a total of 3 orbits.
     59
     60 - L directly orbits K and indirectly orbits J, E, D, C, B, and COM, a total of 7 orbits.
     61
     62 - COM orbits nothing.
     63
     64
     65The total number of direct and indirect orbits in this example is 42.
     66
     67What is the total number of direct and indirect orbits in your map data?
     68
     69
     70