[−][src]Function codetrotter_aoc_2019_solutions::day_06::solve_part_2

pub fn solve_part_2<'a, T>(input_orbit_pairs: &mut T) -> usize where
    T: Iterator<Item = OrbitPair<'a>>,

Day 6, Part Two

https://adventofcode.com/2019/day/6#part2

Now, you just need to figure out how many orbital transfers you (YOU) need to take to get to Santa (SAN).

You start at the object YOU are orbiting; your destination is the object SAN is orbiting. An orbital transfer lets you move from any object to an object orbiting or orbited by that object.

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
K)YOU
I)SAN

Visually, the above map of orbits looks like this:

                          YOU
                         /
        G - H       J - K - L
       /           /
COM - B - C - D - E - F
               \
                I - SAN

In this example, YOU are in orbit around K, and SAN is in orbit around I. To move from K to I, a minimum of 4 orbital transfers are required:

K to J
J to E
E to D
D to I

Afterward, the map of orbits looks like this:

        G - H       J - K - L
       /           /
COM - B - C - D - E - F
               \
                I - SAN
                 \
                  YOU

What is the minimum number of orbital transfers required to move from the object YOU are orbiting to the object SAN is orbiting? (Between the objects they are orbiting - not between YOU and SAN.)

Examples

use codetrotter_aoc_2019_solutions::day_06::{input_generator, solve_part_2};

const EXINPUT: &str =
  "COM)B\n\
   B)C\n\
   C)D\n\
   D)E\n\
   E)F\n\
   B)G\n\
   G)H\n\
   D)I\n\
   E)J\n\
   J)K\n\
   K)L\n\
   K)YOU\n\
   I)SAN";

assert_eq!(solve_part_2(&mut input_generator(EXINPUT)), 4);

Solution

⚠️ SPOILER ALERT ⚠️

use codetrotter_aoc_2019_solutions::day_06::{INPUT, input_generator, solve_part_2};
assert_eq!(solve_part_2(&mut input_generator(INPUT)), 370);