1 files changed, 78 insertions, 0 deletions
diff --git a/2017/src/bin/day_19.rs b/2017/src/bin/day_19.rs
new file mode 100644
index 0000000..b333c98
--- /dev/null
+++ b/2017/src/bin/day_19.rs
@@ -0,0 +1,78 @@
+extern crate advent_of_code_2017;
+use advent_of_code_2017::*;
+
+fn main() {
+    use Direction::*;
+    
+    let args = AdventArgs::init();
+
+    let input: Vec<Vec<char>> = args.input.iter().map(|line| line.chars().collect()).collect();
+
+    let mut position = Point {
+        x: input[0].iter().position(|&c| c == '|').unwrap() as i32,
+        y: 0
+    };
+    
+    let mut direction = Down;
+    let mut path_ended = false;
+    let mut tokens = Vec::new();
+
+    // moving onto the map counts as one, but because of how I'm
+    // counting there's also an off the map step that I shouldn't be
+    // counting at the end. They cancel out.
+    let mut steps_moved = 0;
+
+    while !path_ended {
+        position = position.shift(&direction);
+        steps_moved += 1;
+        
+        match char_at(&input, &position) {
+            '|' | '-' => {
+                //continue as is
+            },
+            ' ' => {
+                path_ended = true;
+            },
+            '+' => {
+                let left_option = char_at(&input, &position.shift(&direction.rotate_left()));
+                let right_option = char_at(&input, &position.shift(&direction.rotate_right()));
+                match (left_option, right_option) {
+                    (' ', ' ') => {
+                        path_ended = true;
+                    },
+                    (_, ' ') => {
+                        direction = direction.rotate_left();
+                    },
+                    (' ', _) => {
+                        direction = direction.rotate_right();
+                    },
+                    _ => {
+                        panic!("Don't know where to go from {:?}", position);
+                    }
+                }
+            },
+            token => {
+                tokens.push(token);
+            }
+        }
+        
+    }
+
+    if args.part == 1 {
+        println!("{}", tokens.iter().collect::<String>());
+    } else {
+        println!("{}", steps_moved);
+    }
+}
+
+fn char_at(input: &Vec<Vec<char>>, position: &Point) -> char {
+    if position.y < 0 ||
+        position.x < 0 ||
+        position.y as usize >= input.len() ||
+        position.x as usize >= input[position.y as usize].len() {
+            ' '
+        } else {
+            input[position.y as usize][position.x as usize]
+        }
+    
+}