1 files changed, 61 insertions, 0 deletions
diff --git a/2016/aoc2/src/main.rs b/2016/aoc2/src/main.rs
new file mode 100644
index 0000000..f4c3bfd
--- /dev/null
+++ b/2016/aoc2/src/main.rs
@@ -0,0 +1,61 @@
+use std::io::BufReader;
+use std::io::prelude::*;
+use std::fs::File;
+
+fn main() {
+    let lines = read_file();
+    let mut current = 5;
+    for line in lines {
+        current = line.chars().fold(current, |current, dir| move_char_hex(current, dir));
+        println!("{:X}", current);
+    }
+}
+
+fn read_file() -> Vec<String> {
+    let file = BufReader::new(File::open("input.txt").unwrap());
+    file.lines()
+        .map(|line| line.unwrap().trim().to_string())
+        .filter(|line| line.len() > 0)
+        .collect()
+}
+
+
+//assume current in 1-9 range, and char is in UDLR
+fn move_char(current: i32, dir: char) -> i32 {
+    match dir {
+        'U' => if current <= 3 { current } else { current - 3},
+        'D' => if current >= 7 { current } else { current + 3},
+        'L' => if current%3 == 1 { current } else { current - 1},
+        'R' => if current%3 == 0 { current } else { current + 1},
+        _ => panic!("Bad direction character")
+    }
+}
+
+//     1
+//   2 3 4
+// 5 6 7 8 9
+//   A B C
+//     D
+fn move_char_hex(current: i32, dir: char) -> i32 {
+    match dir {
+        'U' => match current {
+            1|2|4|5|9 => current,
+            3|13 => current - 2,
+            _  => current - 4
+        },
+        'D' => match current {
+            5|10|13|12|9 => current,
+            1|11 => current + 1,
+            _ => current + 4
+        },
+        'L' => match current {
+            1|2|5|10|13 => current,
+            _ => current - 1
+        },
+        'R' => match current {
+            1|4|9|12|13 => current,
+            _ => current + 1
+        },
+        _ => panic!("Bad direction character")
+    }
+}