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        if first == b'n' {
20            match iter.next().unwrap_or(0) {
21                b'e' => {
22                    iter.next(); // Consume trailing delimeter.
23                    q += 1;
24                    r -= 1;
25                }
26                b'w' => {
27                    iter.next(); // Consume trailing delimeter.
28                    q -= 1;
29                }
30                _ => r -= 1,
31            }
32        } else {
33            match iter.next().unwrap_or(0) {
34                b'e' => {
35                    iter.next(); // Consume trailing delimeter.
36                    q += 1;
37                }
38                b'w' => {
39                    iter.next(); // Consume trailing delimeter.
40                    q -= 1;
41                    r += 1;
42                }
43                _ => r += 1,
44            }
45        }
46
47        // q + r + s = 0, so we can always determine s given the other two.
48        let s = q + r;
49        // Manhattan distance to the center.
50        part_one = (q.abs() + r.abs() + s.abs()) / 2;
51        // Keep track of furthest distance.
52        part_two = part_two.max(part_one);
53    }
54
55    (part_one, part_two)
56}
57
58pub fn part1(input: &Input) -> i32 {
59    input.0
60}
61
62pub fn part2(input: &Input) -> i32 {
63    input.1
64}
aoc/year2017/day11.rs

aoc/year2017/
day11.rs
