Year 2016 Day 1

Author: maneatingape

README.md

@@ -73,6 +73,7 @@ pie
 * [2021](#2021) (11 ms)
 * [2020](#2020) (286 ms)
 * [2019](#2019) (21 ms)
+* [2016](#2016) (in progress)
 * [2015](#2015) (93 ms)
 
 ## 2022
@@ -238,6 +239,12 @@ pie
 | 24 | [Planet of Discord](https://adventofcode.com/2019/day/24) | [Source](src/year2019/day24.rs) | 139 |
 | 25 | [Cryostasis](https://adventofcode.com/2019/day/25) | [Source](src/year2019/day25.rs) | 2721 |
 
+## 2016
+
+| Day | Problem | Solution | Benchmark (μs) |
+| --- | --- | --- | --: |
+| 1 | [No Time for a Taxicab](https://adventofcode.com/2016/day/1) | [Source](src/year2016/day01.rs) | 3 |
+
 ## 2015
 
 ```mermaid

benches/benchmark.rs

@@ -63,6 +63,10 @@ mod year2015 {
     benchmark!(year2015, day25);
 }
 
+mod year2016 {
+    benchmark!(year2016, day01);
+}
+
 mod year2019 {
     benchmark!(year2019, day01);
     benchmark!(year2019, day02);

input/year2016/day01.txt

@@ -0,0 +1 @@
+R5, R4, R2, L3, R1, R1, L4, L5, R3, L1, L1, R4, L2, R1, R4, R4, L2, L2, R4, L4, R1, R3, L3, L1, L2, R1, R5, L5, L1, L1, R3, R5, L1, R4, L5, R5, R1, L185, R4, L1, R51, R3, L2, R78, R1, L4, R188, R1, L5, R5, R2, R3, L5, R3, R4, L1, R2, R2, L4, L4, L5, R5, R4, L4, R2, L5, R2, L1, L4, R4, L4, R2, L3, L4, R2, L3, R3, R2, L2, L3, R4, R3, R1, L4, L2, L5, R4, R4, L1, R1, L5, L1, R3, R1, L2, R1, R1, R3, L4, L1, L3, R2, R4, R2, L2, R1, L5, R3, L3, R3, L1, R4, L3, L3, R4, L2, L1, L3, R2, R3, L2, L1, R4, L3, L5, L2, L4, R1, L4, L4, R3, R5, L4, L1, L1, R4, L2, R5, R1, R1, R2, R1, R5, L1, L3, L5, R2

src/lib.rs

@@ -187,6 +187,11 @@ pub mod year2015 {
     pub mod day25;
 }
 
+/// # Defeat the Easter Bunny to save Christmas.
+pub mod year2016 {
+    pub mod day01;
+}
+
 /// # Rescue Santa from deep space with a solar system adventure.
 pub mod year2019 {
     pub mod day01;

src/main.rs

@@ -101,6 +101,8 @@ fn all_solutions() -> Vec<Solution> {
         solution!(year2015, day23),
         solution!(year2015, day24),
         solution!(year2015, day25),
+        // 2016
+        solution!(year2016, day01),
         // 2019
         solution!(year2019, day01),
         solution!(year2019, day02),

src/year2016/day01.rs

@@ -0,0 +1,53 @@
+//! # No Time for a Taxicab
+//!
+//! The solution is short as it leverages three utility classes, [`hash`] for speedy sets,
+//! [`parse`] for extracting integers from surrounding text and [`point`] for two dimensional
+//! rotations and translations.
+//!
+//! [`hash`]: crate::util::hash
+//! [`parse`]: crate::util::parse
+//! [`point`]: crate::util::point
+use crate::util::hash::*;
+use crate::util::parse::*;
+use crate::util::point::*;
+
+type Pair = (u8, i32);
+
+pub fn parse(input: &str) -> Vec<Pair> {
+    let first = input.bytes().filter(u8::is_ascii_uppercase);
+    let second = input.iter_signed();
+    first.zip(second).collect()
+}
+
+pub fn part1(input: &[Pair]) -> i32 {
+    let mut position = ORIGIN;
+    let mut direction = UP;
+
+    for &(turn, amount) in input {
+        direction =
+            if turn == b'L' { direction.counter_clockwise() } else { direction.clockwise() };
+        position += direction * amount;
+    }
+
+    position.manhattan(ORIGIN)
+}
+
+pub fn part2(input: &[Pair]) -> i32 {
+    let mut position = ORIGIN;
+    let mut direction = UP;
+    let mut visited = FastSet::with_capacity(1000);
+
+    for &(turn, amount) in input {
+        direction =
+            if turn == b'L' { direction.counter_clockwise() } else { direction.clockwise() };
+
+        for _ in 0..amount {
+            position += direction;
+            if !visited.insert(position) {
+                return position.manhattan(ORIGIN);
+            }
+        }
+    }
+
+    unreachable!()
+}

tests/test.rs

@@ -56,6 +56,10 @@ mod year2015 {
     mod day25_test;
 }
 
+mod year2016 {
+    mod day01_test;
+}
+
 mod year2019 {
     mod day01_test;
     mod day02_test;

tests/year2016/day01_test.rs

@@ -0,0 +1,16 @@
+use aoc::year2016::day01::*;
+
+const FIRST_EXAMPLE: &str = "R5, L5, R5, R3";
+const SECOND_EXAMPLE: &str = "R8, R4, R4, R8";
+
+#[test]
+fn part1_test() {
+    let input = parse(FIRST_EXAMPLE);
+    assert_eq!(part1(&input), 12);
+}
+
+#[test]
+fn part2_test() {
+    let input = parse(SECOND_EXAMPLE);
+    assert_eq!(part2(&input), 4);
+}