day09 finished

data/day09/example01.txt

@@ -0,0 +1,8 @@
+R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2

data/day09/example02.txt

@@ -0,0 +1,8 @@
+R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20

src/days/day09/mod.rs

@@ -0,0 +1,152 @@
+use super::template::{DayTrait, ResultType};
+use crate::common::{direction::Direction, pos::Pos};
+use std::{collections::HashSet, num::ParseIntError};
+use thiserror::Error;
+
+const DAY_NUMBER: usize = 9;
+
+pub struct Day;
+
+impl DayTrait for Day {
+    fn get_day_number(&self) -> usize {
+        DAY_NUMBER
+    }
+
+    fn part1(&self, lines: &[String]) -> anyhow::Result<ResultType> {
+        let commands = parse_commands(lines)?;
+        let mut rope = Rope::create(2);
+        let result = rope.run(&commands);
+        Ok(ResultType::Integer(result))
+    }
+
+    fn part2(&self, lines: &[String]) -> anyhow::Result<ResultType> {
+        let commands = parse_commands(lines)?;
+        let mut rope = Rope::create(10);
+        let result = rope.run(&commands);
+        Ok(ResultType::Integer(result))
+    }
+}
+
+#[derive(Debug, Error)]
+enum RopeError {
+    #[error("Not a legal command {0}")]
+    CommandUnknown(String),
+
+    #[error["not a legal Direction {0}"]]
+    DirectionUnknown(String),
+
+    #[error("Not a legal Integer")]
+    StepParseError(#[from] ParseIntError),
+}
+
+fn parse_commands(lines: &[String]) -> Result<Vec<(Direction, usize)>, RopeError> {
+    lines.iter().map(parse_line).collect::<Result<_, _>>()
+}
+
+fn parse_line(line: &String) -> Result<(Direction, usize), RopeError> {
+    match line.split_whitespace().collect::<Vec<_>>()[..] {
+        [direction, steps] => {
+            let direction = match direction {
+                "U" => Direction::North,
+                "D" => Direction::South,
+                "R" => Direction::East,
+                "L" => Direction::West,
+                _ => {
+                    return Err(RopeError::DirectionUnknown(direction.to_owned()));
+                }
+            };
+            let steps = steps.parse()?;
+            Ok((direction, steps))
+        }
+        _ => Err(RopeError::CommandUnknown(line.to_owned())),
+    }
+}
+
+fn get_closer(first: Pos<i32>, second: Pos<i32>) -> Option<Pos<i32>> {
+    let diff = second - first;
+    if diff.x().abs() <= 1 && diff.y().abs() <= 1 {
+        None
+    } else {
+        Some(Pos::new(diff.x().signum(), diff.y().signum()))
+    }
+}
+
+#[derive(Debug)]
+struct Rope {
+    head: Pos<i32>,
+    knots: Vec<Pos<i32>>,
+}
+
+impl Rope {
+    pub fn create(length: usize) -> Self {
+        assert!(length >= 2);
+        Rope {
+            head: Pos::new(0, 0),
+            knots: vec![Pos::new(0, 0); length - 1],
+        }
+    }
+
+    /**
+     * Moves the head one step into the given direction
+     * returns true if the whole rope moved, otherwise false
+     */
+    pub fn move_rope(&mut self, head_direction: Direction) -> bool {
+        self.head = self.head + head_direction;
+        let mut prev = self.head;
+        let mut knots_unmoved = self.knots.len();
+
+        for knot in self.knots.iter_mut() {
+            if let Some(diff) = get_closer(*knot, prev) {
+                *knot = *knot + diff;
+                prev = *knot;
+                knots_unmoved -= 1;
+            } else {
+                break;
+            }
+        }
+        knots_unmoved == 0
+    }
+
+    pub fn run(&mut self, commands: &[(Direction, usize)]) -> i64 {
+        let mut tail_visited = HashSet::new();
+        tail_visited.insert(self.knots.last().copied().unwrap());
+
+        for (direction, steps) in commands {
+            for _ in 0..*steps {
+                if self.move_rope(*direction) {
+                    tail_visited.insert(self.knots.last().copied().unwrap());
+                }
+            }
+        }
+        tail_visited.len() as i64
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::common::file::read_lines;
+    use anyhow::Result;
+
+    #[test]
+    fn test_part1() -> Result<()> {
+        let day = Day {};
+        let lines = read_lines(day.get_day_number(), "example01.txt")?;
+        let expected = ResultType::Integer(13);
+        let result = day.part1(&lines)?;
+        assert_eq!(result, expected);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_part2() -> Result<()> {
+        let day = Day {};
+        let lines = read_lines(day.get_day_number(), "example02.txt")?;
+        let expected = ResultType::Integer(36);
+        let result = day.part2(&lines)?;
+        assert_eq!(result, expected);
+
+        Ok(())
+    }
+}

src/days/mod.rs

@@ -6,6 +6,7 @@ mod day05;
 mod day06;
 mod day07;
 mod day08;
+mod day09;
 mod template;
 
 pub use template::DayTrait;
@@ -15,7 +16,7 @@ pub mod day_provider {
     use super::*;
     use thiserror::Error;
 
-    const MAX_DAY: usize = 8;
+    const MAX_DAY: usize = 9;
 
     pub fn get_day(day_num: usize) -> Result<Box<dyn DayTrait>, ProviderError> {
         match day_num {
@@ -27,6 +28,7 @@ pub mod day_provider {
             6 => Ok(Box::new(day06::Day)),
             7 => Ok(Box::new(day07::Day)),
             8 => Ok(Box::new(day08::Day)),
+            9 => Ok(Box::new(day09::Day)),
             _ => Err(ProviderError::InvalidNumber(day_num)),
         }
     }