aoc/year2017/
day11.rs

1//! # Hex Ed
2//!
3//! Hex grid parsing and navigation uses
4//! [Axial Coordinates](https://www.redblobgames.com/grids/hexagons/#coordinates-cube)
5//! exactly as described in the excellent [Red Blob Games](https://www.redblobgames.com/) blog.
6//!
7//! As mentioned in the blog, the Manhattan distance to the center has the formula
8//! `(q.abs() + r.abs() + s.abs()) / 2`
9type Input = (i32, i32);
10
11pub fn parse(input: &str) -> Input {
12    let mut iter = input.bytes();
13    let mut q: i32 = 0;
14    let mut r: i32 = 0;
15    let mut part_one = 0;
16    let mut part_two = 0;
17
18    while let Some(first) = iter.next() {
19        match first {
20            b'n' => match iter.next().unwrap_or(0) {
21                b'e' => {
22                    q += 1;
23                    r -= 1;
24                }
25                b'w' => q -= 1,
26                _ => r -= 1,
27            },
28            b's' => match iter.next().unwrap_or(0) {
29                b'e' => q += 1,
30                b'w' => {
31                    q -= 1;
32                    r += 1;
33                }
34                _ => r += 1,
35            },
36            _ => (),
37        }
38
39        // q + r + s = 0, so we can always determine s given the other two.
40        let s = q + r;
41        // Manhattan distance to the center.
42        part_one = (q.abs() + r.abs() + s.abs()) / 2;
43        // Keep track of furthest distance.
44        part_two = part_two.max(part_one);
45    }
46
47    (part_one, part_two)
48}
49
50pub fn part1(input: &Input) -> i32 {
51    input.0
52}
53
54pub fn part2(input: &Input) -> i32 {
55    input.1
56}
aoc/year2017/day11.rs

aoc/year2017/
day11.rs
