implement day 7

src/day_07/mod.rs

@@ -0,0 +1,70 @@
+mod model;
+mod parsing;
+
+use aoc_runner_derive::{aoc, aoc_generator};
+pub use model::CrabSub;
+pub use parsing::parse_crab_sub_swarm;
+use yap::IntoTokens;
+
+#[aoc_generator(day7)]
+pub fn parse_input(input: &str) -> Vec<CrabSub> {
+    parse_crab_sub_swarm(&mut input.into_tokens())
+}
+
+#[aoc(day7, part1)]
+pub fn part1(input: &[CrabSub]) -> usize {
+    solve(input, &|x| x)
+}
+
+fn bounds(input: &[CrabSub]) -> (usize, usize) {
+    let locations: Vec<usize> = input.iter().map(|sub| sub.location).collect();
+    (
+        *locations.iter().min().unwrap(),
+        *locations.iter().max().unwrap(),
+    )
+}
+
+pub fn solve(input: &[CrabSub], fuel_calc: &dyn Fn(usize) -> usize) -> usize {
+    let mut req_fuel = usize::MAX;
+    let (min, max) = bounds(input);
+    for i in min..=max {
+        let mut new_req_fuel = 0;
+        for sub in input.iter() {
+            new_req_fuel += fuel_calc((i as isize - sub.location as isize).abs() as usize);
+        }
+        if req_fuel > new_req_fuel {
+            req_fuel = new_req_fuel;
+        }
+    }
+    req_fuel
+}
+
+#[aoc(day7, part2)]
+pub fn part2(input: &[CrabSub]) -> usize {
+    solve(input, &|distance| (1..=distance).sum())
+}
+
+#[cfg(test)]
+mod test {
+    const EXAMPLE_INPUT: &str = "16,1,2,0,4,2,7,1,2,14";
+    const RESULT_PART_1: usize = 37;
+    const RESULT_PART_2: usize = 168;
+
+    #[test]
+    fn part1_example() {
+        let result = super::part1(&super::parse_input(EXAMPLE_INPUT));
+        assert_eq!(result, RESULT_PART_1);
+    }
+
+    #[test]
+    fn part2_example() {
+        let result = super::part2(&super::parse_input(EXAMPLE_INPUT));
+        assert_eq!(result, RESULT_PART_2);
+    }
+
+    #[test]
+    fn parse_example() {
+        let example = super::parse_input(EXAMPLE_INPUT);
+        assert_eq!(example.len(), 10);
+    }
+}

src/day_07/model.rs

@@ -0,0 +1,4 @@
+#[derive(Debug, PartialEq, Copy, Clone)]
+pub struct CrabSub {
+    pub location: usize,
+}

src/day_07/parsing.rs

@@ -0,0 +1,35 @@
+use super::CrabSub;
+use crate::parsing::parse_number;
+use yap::Tokens;
+
+pub fn parse_crab_sub(tokens: &mut impl Tokens<Item = char>) -> Option<CrabSub> {
+    parse_number(tokens).map(|num| CrabSub { location: num })
+}
+
+pub fn parse_crab_sub_swarm(tokens: &mut impl Tokens<Item = char>) -> Vec<CrabSub> {
+    tokens
+        .sep_by(|t| parse_crab_sub(t), |t| t.token(','))
+        .collect()
+}
+
+#[cfg(test)]
+mod test {
+    use super::super::CrabSub;
+    use yap::IntoTokens;
+
+    #[test]
+    fn parse_crab_sub() {
+        assert_eq!(
+            Some(CrabSub { location: 1 }),
+            super::parse_crab_sub(&mut "1".into_tokens())
+        );
+    }
+
+    #[test]
+    fn parse_crab_sub_swarm() {
+        assert_eq!(
+            10,
+            super::parse_crab_sub_swarm(&mut "16,1,2,0,4,2,7,1,2,14".into_tokens()).len()
+        );
+    }
+}

src/lib.rs

@@ -8,5 +8,6 @@ pub mod day_03;
 pub mod day_04;
 pub mod day_05;
 pub mod day_06;
+pub mod day_07;
 
 aoc_lib! { year = 2021 }