2017/10-11

2017/11/src/main.rs

@@ -0,0 +1,134 @@
+use std::str::FromStr;
+use std::io::{self, Read};
+
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+enum Direction {
+    Nw,
+    N,
+    Ne,
+    Se,
+    S,
+    Sw,
+}
+
+impl Direction {
+    fn delta(&self) -> (i32, i32) {
+        match *self {
+            Direction::Nw => (-1, 1),
+            Direction::N => (0, 1),
+            Direction::Ne => (1, 0),
+            Direction::Se => (1, -1),
+            Direction::S => (0, -1),
+            Direction::Sw => (-1, 0),
+        }
+    }
+}
+
+impl FromStr for Direction {
+    type Err = ();
+
+    fn from_str(input: &str) -> Result<Direction, Self::Err> {
+        match input {
+            "nw" => Ok(Direction::Nw),
+            "n" => Ok(Direction::N),
+            "ne" => Ok(Direction::Ne),
+            "se" => Ok(Direction::Se),
+            "s" => Ok(Direction::S),
+            "sw" => Ok(Direction::Sw),
+            _ => Err(()),
+        }
+    }
+}
+
+
+fn parse(input: &str) -> Vec<Direction> {
+    input
+        .split(',')
+        .filter_map(|dir| Direction::from_str(dir).ok())
+        .collect::<Vec<_>>()
+}
+
+fn distance(a: (i32, i32), b: (i32, i32)) -> usize {
+    let dx = b.0 - a.0;
+    let dy = b.1 - a.1;
+
+    if dx.signum() == dy.signum() {
+        (dx + dy).abs() as usize
+    } else {
+        usize::max(dx.abs() as usize, dy.abs() as usize)
+    }
+}
+
+fn main() {
+    let mut input = String::new();
+
+    io::stdin()
+        .read_to_string(&mut input)
+        .expect("faild to read input");
+
+    for line in input.lines().filter(|line| !line.is_empty()) {
+        let position = parse(line)
+            .iter()
+            .map(|dir| dir.delta())
+            .fold((0, 0), |p, d| (p.0 + d.0, p.1 + d.1));
+
+        println!("part_one={}", distance((0, 0), position));
+
+        let max = parse(line)
+            .iter()
+            .map(|dir| dir.delta())
+            .scan((0, 0), |p, d| {
+                p.0 += d.0;
+                p.1 += d.1;
+
+                Some(distance((0, 0), *p))
+            })
+            .max();
+
+        if let Some(distance) = max {
+            println!("part_two={}", distance);
+        }
+    }
+}
+
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+
+    #[test]
+    fn test_direction() {
+        assert_eq!("nw".parse(), Ok(Direction::Nw));
+        assert_eq!("n".parse(), Ok(Direction::N));
+        assert_eq!("ne".parse(), Ok(Direction::Ne));
+        assert_eq!("se".parse(), Ok(Direction::Se));
+        assert_eq!("s".parse(), Ok(Direction::S));
+        assert_eq!("sw".parse(), Ok(Direction::Sw));
+    }
+
+    #[test]
+    fn test_parse() {
+        assert_eq!(
+            parse("ne,ne,ne"),
+            vec![Direction::Ne, Direction::Ne, Direction::Ne]
+        );
+        assert_eq!(
+            parse("ne,ne,sw,sw"),
+            vec![Direction::Ne, Direction::Ne, Direction::Sw, Direction::Sw]
+        );
+    }
+
+    #[test]
+    fn test_distance() {
+        assert_eq!(distance((0, 0), (0, 3)), 3);
+        assert_eq!(distance((0, 0), (-3, 3)), 3);
+        assert_eq!(distance((0, 0), (-3, 0)), 3);
+        assert_eq!(distance((0, 0), (0, -3)), 3);
+        assert_eq!(distance((0, 0), (3, -3)), 3);
+        assert_eq!(distance((0, 0), (3, 0)), 3);
+
+        assert_eq!(distance((0, 0), (-2, 1)), 2);
+    }
+}