feat: impl day 6

4 files changed, 130 insertions, 1 deletions

diff --git a/input/day_06.txt b/input/day_06.txt
new file mode 100644
index 0000000..45d4be3
--- /dev/null
+++ b/input/day_06.txt
@@ -0,0 +1,2 @@
+Time:        40     82     91     66
+Distance:   277   1338   1349   1063
diff --git a/src/day_06.rs b/src/day_06.rs
new file mode 100644
index 0000000..2b988a3
--- /dev/null
+++ b/src/day_06.rs
@@ -0,0 +1,122 @@
+use crate::{Problem, Solution};
+
+pub struct Day06;
+
+impl Problem for Day06 {
+    const DAY: u8 = 6;
+
+    const INPUT: &'static str = include_str!("../input/day_06.txt");
+}
+
+impl Solution for Day06 {
+    type Answer1 = usize;
+
+    type Answer2 = usize;
+
+    fn part_1(input: &str) -> anyhow::Result<Self::Answer1> {
+        let (time, dist) = input.split_once('\n').expect("Invalid input lines");
+        let races = time
+            .split_whitespace()
+            .skip(1)
+            .zip(dist.split_whitespace().skip(1))
+            .map(TryFrom::try_from)
+            .try_collect::<Vec<Race>>()?;
+
+        races
+            .iter()
+            .map(Race::wins)
+            .reduce(|acc, n| acc * n)
+            .ok_or(anyhow::format_err!("Failed to find race"))
+    }
+
+    fn part_2(input: &str) -> anyhow::Result<Self::Answer2> {
+        let race: Race = input.parse()?;
+        Ok(race.wins())
+    }
+}
+
+#[derive(Debug)]
+struct Race {
+    time: usize,
+    dist: usize,
+}
+
+impl Race {
+    fn run(&self, speed: usize) -> bool {
+        (speed * (self.time - speed)) > self.dist
+    }
+
+    fn wins(&self) -> usize {
+        let mut count = 0;
+        for speed in 1..self.time {
+            if self.run(speed) {
+                count += 1;
+            } else if count > 0 {
+                break;
+            }
+        }
+        count
+    }
+}
+
+impl TryFrom<(&str, &str)> for Race {
+    type Error = std::num::ParseIntError;
+
+    fn try_from((time, dist): (&str, &str)) -> Result<Self, Self::Error> {
+        Ok(Self {
+            time: time.parse()?,
+            dist: dist.parse()?,
+        })
+    }
+}
+
+impl std::str::FromStr for Race {
+    type Err = anyhow::Error;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let (time, dist) = s
+            .trim()
+            .split_once('\n')
+            .ok_or(anyhow::format_err!("Invalid race format"))?;
+
+        let time = time
+            .strip_prefix("Time: ")
+            .ok_or(anyhow::format_err!("Invalid time format"))?
+            .chars()
+            .filter(|c| *c != ' ')
+            .collect::<String>()
+            .trim()
+            .parse()?;
+
+        let dist = dist
+            .strip_prefix("Distance: ")
+            .ok_or(anyhow::format_err!("Invalid distance format"))?
+            .chars()
+            .filter(|c| *c != ' ')
+            .collect::<String>()
+            .trim()
+            .parse()?;
+
+        Ok(Race { time, dist })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT: &str = indoc::indoc! {"
+        Time:      7  15   30
+        Distance:  9  40  200
+    "};
+
+    #[test]
+    fn test_part_1() -> anyhow::Result<()> {
+        Ok(assert_eq!(288, Day06::part_1(INPUT)?))
+    }
+
+    #[test]
+    fn test_part_2() -> anyhow::Result<()> {
+        Ok(assert_eq!(71503, Day06::part_2(INPUT)?))
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 7563500..8875ecc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -6,6 +6,7 @@ pub mod day_02;
 pub mod day_03;
 pub mod day_04;
 pub mod day_05;
+pub mod day_06;
 
 pub trait Problem {
     const DAY: u8;
diff --git a/src/main.rs b/src/main.rs
index feae755..1c93d0a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,4 +1,7 @@
-use aoc_2023::{day_01::Day01, day_02::Day02, day_03::Day03, day_04::Day04, Solution, day_05::Day05};
+use aoc_2023::{
+    day_01::Day01, day_02::Day02, day_03::Day03, day_04::Day04, day_05::Day05, day_06::Day06,
+    Solution,
+};
 
 fn main() -> anyhow::Result<()> {
     Day01::solve()?;
@@ -6,6 +9,7 @@ fn main() -> anyhow::Result<()> {
     Day03::solve()?;
     Day04::solve()?;
     Day05::solve()?;
+    Day06::solve()?;
 
     Ok(())
 }