Added Solution for 2020 day 12

.gitignore

@@ -5,3 +5,4 @@ day00
 **/dbg.log
 **/2
 **/.vimdid
+**/rust-analyzer.core

2020/day12_rain_risk/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day12_rain_risk"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2020/day12_rain_risk/challenge.txt

@@ -0,0 +1,77 @@
+Your ferry made decent progress toward the island, but the storm came in faster than anyone expected. The ferry needs to take *evasive actions*!
+
+Unfortunately, the ship's navigation computer seems to be malfunctioning; rather than giving a route directly to safety, it produced extremely circuitous instructions. When the captain uses the [PA system](https://en.wikipedia.org/wiki/Public_address_system) to ask if anyone can help, you quickly volunteer.
+
+The navigation instructions (your puzzle input) consists of a sequence of single-character *actions* paired with integer input *values*. After staring at them for a few minutes, you work out what they probably mean:
+
+* Action *`N`* means to move *north* by the given value.
+* Action *`S`* means to move *south* by the given value.
+* Action *`E`* means to move *east* by the given value.
+* Action *`W`* means to move *west* by the given value.
+* Action *`L`* means to turn *left* the given number of degrees.
+* Action *`R`* means to turn *right* the given number of degrees.
+* Action *`F`* means to move *forward* by the given value in the direction the ship is currently facing.
+
+The ship starts by facing *east*. Only the `L` and `R` actions change the direction the ship is facing. (That is, if the ship is facing east and the next instruction is `N10`, the ship would move north 10 units, but would still move east if the following action were `F`.)
+
+For example:
+
+```
+F10
+N3
+F7
+R90
+F11
+
+```
+
+These instructions would be handled as follows:
+
+* `F10` would move the ship 10 units east (because the ship starts by facing east) to *east 10, north 0*.
+* `N3` would move the ship 3 units north to *east 10, north 3*.
+* `F7` would move the ship another 7 units east (because the ship is still facing east) to *east 17, north 3*.
+* `R90` would cause the ship to turn right by 90 degrees and face *south*; it remains at *east 17, north 3*.
+* `F11` would move the ship 11 units south to *east 17, south 8*.
+
+At the end of these instructions, the ship's [Manhattan distance](https://en.wikipedia.org/wiki/Manhattan_distance) (sum of the absolute values of its east/west position and its north/south position) from its starting position is `17 + 8` = *`25`*.
+
+Figure out where the navigation instructions lead. *What is the Manhattan distance between that location and the ship's starting position?*
+
+Your puzzle answer was `1032`.
+
+\--- Part Two ---
+----------
+
+Before you can give the destination to the captain, you realize that the actual action meanings were printed on the back of the instructions the whole time.
+
+Almost all of the actions indicate how to move a *waypoint* which is relative to the ship's position:
+
+* Action *`N`* means to move the waypoint *north* by the given value.
+* Action *`S`* means to move the waypoint *south* by the given value.
+* Action *`E`* means to move the waypoint *east* by the given value.
+* Action *`W`* means to move the waypoint *west* by the given value.
+* Action *`L`* means to rotate the waypoint around the ship *left* (*counter-clockwise*) the given number of degrees.
+* Action *`R`* means to rotate the waypoint around the ship *right* (*clockwise*) the given number of degrees.
+* Action *`F`* means to move *forward* to the waypoint a number of times equal to the given value.
+
+The waypoint starts *10 units east and 1 unit north* relative to the ship. The waypoint is relative to the ship; that is, if the ship moves, the waypoint moves with it.
+
+For example, using the same instructions as above:
+
+* `F10` moves the ship to the waypoint 10 times (a total of *100 units east and 10 units north*), leaving the ship at *east 100, north 10*. The waypoint stays 10 units east and 1 unit north of the ship.
+* `N3` moves the waypoint 3 units north to *10 units east and 4 units north of the ship*. The ship remains at *east 100, north 10*.
+* `F7` moves the ship to the waypoint 7 times (a total of *70 units east and 28 units north*), leaving the ship at *east 170, north 38*. The waypoint stays 10 units east and 4 units north of the ship.
+* `R90` rotates the waypoint around the ship clockwise 90 degrees, moving it to *4 units east and 10 units south of the ship*. The ship remains at *east 170, north 38*.
+* `F11` moves the ship to the waypoint 11 times (a total of *44 units east and 110 units south*), leaving the ship at *east 214, south 72*. The waypoint stays 4 units east and 10 units south of the ship.
+
+After these operations, the ship's Manhattan distance from its starting position is `214 + 72` = *`286`*.
+
+Figure out where the navigation instructions actually lead. *What is the Manhattan distance between that location and the ship's starting position?*
+
+Your puzzle answer was `156735`.
+
+Both parts of this puzzle are complete! They provide two gold stars: \*\*
+
+At this point, you should [return to your Advent calendar](/2020) and try another puzzle.
+
+If you still want to see it, you can [get your puzzle input](12/input).

2020/day12_rain_risk/src/lib.rs

@@ -0,0 +1,166 @@
+use core::fmt::Display;
+use std::num::ParseIntError;
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum ParseError {
+    ParseIntError(std::num::ParseIntError),
+    LineMalformed(String),
+}
+
+impl From<ParseIntError> for ParseError {
+    fn from(value: ParseIntError) -> Self {
+        Self::ParseIntError(value)
+    }
+}
+
+impl Display for ParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::ParseIntError(e) => write!(f, "Unable to parse into integer: {e}"),
+            Self::LineMalformed(v) => write!(f, "Line is malformed: {v}"),
+        }
+    }
+}
+
+enum Action {
+    North(isize),
+    South(isize),
+    East(isize),
+    West(isize),
+    Left(isize),
+    Right(isize),
+    Forwd(isize),
+}
+
+impl TryFrom<&str> for Action {
+    type Error = ParseError;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        match value.chars().next() {
+            Some('N') => Ok(Self::North(value[1..].parse()?)),
+            Some('S') => Ok(Self::South(value[1..].parse()?)),
+            Some('E') => Ok(Self::East(value[1..].parse()?)),
+            Some('W') => Ok(Self::West(value[1..].parse()?)),
+            Some('L') => Ok(Self::Left(value[1..].parse()?)),
+            Some('R') => Ok(Self::Right(value[1..].parse()?)),
+            Some('F') => Ok(Self::Forwd(value[1..].parse()?)),
+            _ => Err(Self::Error::LineMalformed(value.to_string())),
+        }
+    }
+}
+
+struct Ferry {
+    pos: (isize, isize),
+    dir: isize,
+    waypoint: (isize, isize),
+}
+
+impl Default for Ferry {
+    fn default() -> Self {
+        Self {
+            pos: (0, 0),
+            dir: 0,
+            waypoint: (10, -1),
+        }
+    }
+}
+
+impl Ferry {
+    fn perform_action(&mut self, action: &Action) {
+        match action {
+            Action::North(i) => self.pos.1 -= i,
+            Action::South(i) => self.pos.1 += i,
+            Action::East(i) => self.pos.0 += i,
+            Action::West(i) => self.pos.0 -= i,
+            Action::Left(i) => self.dir = (self.dir-i) % 360,
+            Action::Right(i) => self.dir = (self.dir+i) % 360,
+            Action::Forwd(i) => match self.dir {
+                -90 | 270 => self.pos.1 -= i,
+                90 | -270 => self.pos.1 += i,
+                0 => self.pos.0 += i,
+                180 | -180 => self.pos.0 -= i,
+                _ => panic!("Trying to move in unknown direction {}", self.dir),
+            },
+        }
+    }
+
+    fn perform_waypoint_action(&mut self, action: &Action) {
+        match action {
+            Action::North(i) => self.waypoint.1 -= i,
+            Action::South(i) => self.waypoint.1 += i,
+            Action::East(i) => self.waypoint.0 += i,
+            Action::West(i) => self.waypoint.0 -= i,
+            Action::Left(i) => match i {
+                90 => {
+                    let x = self.waypoint.0;
+                    self.waypoint.0 = self.waypoint.1;
+                    self.waypoint.1 = -x;
+                },
+                180 => {
+                    self.waypoint.0 *= -1;
+                    self.waypoint.1 *= -1;
+                },
+                270 => {
+                    let x = self.waypoint.0;
+                    self.waypoint.0 = -self.waypoint.1;
+                    self.waypoint.1 = x;
+                },
+                _ => panic!("Trying to turn left by unknown amount {i}"),
+            },
+            Action::Right(i) => match i {
+                90 => {
+                    let x = self.waypoint.0;
+                    self.waypoint.0 = -self.waypoint.1;
+                    self.waypoint.1 = x;
+                },
+                180 => {
+                    self.waypoint.0 *= -1;
+                    self.waypoint.1 *= -1;
+                },
+                270 => {
+                    let x = self.waypoint.0;
+                    self.waypoint.0 = self.waypoint.1;
+                    self.waypoint.1 = -x;
+                },
+                _ => panic!("Trying to turn right by unknown amount {i}"),
+            },
+            Action::Forwd(i) => {
+                self.pos.0 += i*self.waypoint.0;
+                self.pos.1 += i*self.waypoint.1;
+            },
+        }
+    }
+}
+
+pub fn run(input: &str) -> Result<(usize, usize), ParseError> {
+    let mut ferry = Ferry::default();
+    let actions: Vec<_> = input.lines().map(Action::try_from).collect::<Result<Vec<_>, _>>()?;
+    actions.iter().for_each(|a| ferry.perform_action(a));
+    let first = ferry.pos.0.unsigned_abs() + ferry.pos.1.unsigned_abs();
+    ferry = Ferry::default();
+    actions.iter().for_each(|a| ferry.perform_waypoint_action(a));
+    let second = ferry.pos.0.unsigned_abs() + ferry.pos.1.unsigned_abs();
+    Ok((first, second))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs::read_to_string;
+
+    fn read_file(name: &str) -> String {
+        read_to_string(name).expect(&format!("Unable to read file: {name}")[..]).trim().to_string()
+    }
+
+    #[test]
+    fn test_sample() {
+        let sample_input = read_file("tests/sample_input");
+        assert_eq!(run(&sample_input), Ok((25, 286)));
+    }
+
+    #[test]
+    fn test_challenge() {
+        let challenge_input = read_file("tests/challenge_input");
+        assert_eq!(run(&challenge_input), Ok((1032, 156735)));
+    }
+}

2020/day12_rain_risk/tests/challenge_input

@@ -0,0 +1,796 @@
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2020/day12_rain_risk/tests/sample_input

@@ -0,0 +1,5 @@
+F10
+N3
+F7
+R90
+F11