1 files changed, 78 insertions, 0 deletions
diff --git a/2016/src/bin/day01.rs b/2016/src/bin/day01.rs
new file mode 100644
index 0000000..c596099
--- /dev/null
+++ b/2016/src/bin/day01.rs
@@ -0,0 +1,78 @@
+use std::collections::HashSet;
+use std::io::{self, Read};
+use std::ops::Add;
+
+#[derive(Clone, Copy, PartialEq, Eq, Hash)]
+struct Point(i32, i32);
+
+impl Point {
+    fn left(self) -> Self {
+        Point(self.1, -self.0)
+    }
+
+    fn right(self) -> Self {
+        Point(-self.1, self.0)
+    }
+
+    fn distance(self) -> i32 {
+        self.0.abs() + self.1.abs()
+    }
+}
+
+impl Add for Point {
+    type Output = Self;
+
+    fn add(self, rhs: Self) -> Self {
+        Point(self.0 + rhs.0, self.1 + rhs.1)
+    }
+}
+
+fn solve(input: &str) -> (i32, Option<i32>) {
+    let mut position = Point(0, 0);
+    let mut direction = Point(0, -1);
+    let mut visited = HashSet::new();
+    let mut collision = None;
+
+    for instruction in input.trim().split(", ") {
+        let (turn, count) = instruction.split_at(1);
+
+        if turn == "L" {
+            direction = direction.left();
+        } else {
+            direction = direction.right();
+        }
+
+        let count: i32 = count.parse().unwrap();
+        for _ in 0..count {
+            position = position + direction;
+            if collision.is_none() && !visited.insert(position) {
+                collision = Some(position);
+            }
+        }
+    }
+
+    (position.distance(), collision.map(Point::distance))
+}
+
+fn main() {
+    let mut input = String::new();
+    io::stdin().read_to_string(&mut input).unwrap();
+
+    let (part1, part2) = solve(&input);
+    println!("Part 1: {}", part1);
+    if let Some(part2) = part2 {
+        println!("Part 2: {}", part2);
+    }
+}
+
+#[test]
+fn part1() {
+    assert_eq!(5, solve("R2, L3").0);
+    assert_eq!(2, solve("R2, R2, R2").0);
+    assert_eq!(12, solve("R5, L5, R5, R3").0);
+}
+
+#[test]
+fn part2() {
+    assert_eq!(Some(4), solve("R8, R4, R4, R8").1);
+}