Year 2018 Day 11

Author: maneatingape

README.md

@@ -250,6 +250,7 @@ pie
 | 8 | [I Heard You Like Registers](https://adventofcode.com/2017/day/8) | [Source](src/year2017/day08.rs) | 46 |
 | 9 | [Stream Processing](https://adventofcode.com/2017/day/9) | [Source](src/year2017/day09.rs) | 13 |
 | 10 | [Knot Hash](https://adventofcode.com/2017/day/10) | [Source](src/year2017/day10.rs) | 112 |
+| 11 | [Hex Ed](https://adventofcode.com/2017/day/11) | [Source](src/year2017/day11.rs) | 20 |
 
 ## 2016
 

benches/benchmark.rs

@@ -102,6 +102,7 @@ mod year2017 {
     benchmark!(year2017, day08);
     benchmark!(year2017, day09);
     benchmark!(year2017, day10);
+    benchmark!(year2017, day11);
 }
 
 mod year2019 {

input/year2017/day11.txt

@@ -91,6 +91,7 @@ pub mod year2017 {
     pub mod day08;
     pub mod day09;
     pub mod day10;
+    pub mod day11;
 }
 
 /// # Rescue Santa from deep space with a solar system adventure.

src/lib.rs

@@ -152,6 +152,7 @@ fn year2017() -> Vec<Solution> {
         solution!(year2017, day08),
         solution!(year2017, day09),
         solution!(year2017, day10),
+        solution!(year2017, day11),
     ]
 }
 

src/main.rs

@@ -0,0 +1,56 @@
+//! # Hex Ed
+//!
+//! Hex grid parsing and navigation uses
+//! [Axial Coordinates](https://www.redblobgames.com/grids/hexagons/#coordinates-cube)
+//! exactly as described in the excellent [Red Blob Games](https://www.redblobgames.com/) blog.
+//!
+//! As mentioned in the blog, the Manhattan distance to the center has the formula
+//! `(q.abs() + r.abs() + s.abs()) / 2`
+type Input = (i32, i32);
+
+pub fn parse(input: &str) -> Input {
+    let mut iter = input.bytes();
+    let mut q: i32 = 0;
+    let mut r: i32 = 0;
+    let mut part_one = 0;
+    let mut part_two = 0;
+
+    while let Some(first) = iter.next() {
+        match first {
+            b'n' => match iter.next().unwrap_or(0) {
+                b'e' => {
+                    q += 1;
+                    r -= 1;
+                }
+                b'w' => q -= 1,
+                _ => r -= 1,
+            },
+            b's' => match iter.next().unwrap_or(0) {
+                b'e' => q += 1,
+                b'w' => {
+                    q -= 1;
+                    r += 1;
+                }
+                _ => r += 1,
+            },
+            _ => (),
+        }
+
+        // q + r + s = 0, so we can always determine s given the other two.
+        let s = q + r;
+        // Manhattan distance to the center.
+        part_one = (q.abs() + r.abs() + s.abs()) / 2;
+        // Keep track of furthest distance.
+        part_two = part_two.max(part_one);
+    }
+
+    (part_one, part_two)
+}
+
+pub fn part1(input: &Input) -> i32 {
+    input.0
+}
+
+pub fn part2(input: &Input) -> i32 {
+    input.1
+}

src/year2017/day11.rs

@@ -95,6 +95,7 @@ mod year2017 {
     mod day08_test;
     mod day09_test;
     mod day10_test;
+    mod day11_test;
 }
 
 mod year2019 {

tests/test.rs

@@ -0,0 +1,15 @@
+use aoc::year2017::day11::*;
+
+const EXAMPLE: &str = "se,sw,se,sw,sw,s,n";
+
+#[test]
+fn part1_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part1(&input), 3);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(EXAMPLE);
+    assert_eq!(part2(&input), 4);
+}