1 files changed, 91 insertions, 0 deletions
diff --git a/aoc2/src/main.rs b/aoc2/src/main.rs
new file mode 100644
index 0000000..e3188e7
--- /dev/null
+++ b/aoc2/src/main.rs
@@ -0,0 +1,91 @@
+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_2(current, dir));
+        println!("{}", 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_2(current: char, dir: char) -> char {
+    match dir {
+        'U' => match current {
+            '1'|'2'|'4'|'5'|'9' => current,
+            '3' => '1',
+            '6' => '2',
+            '7' => '3',
+            '8' => '4',
+            'A' => '6',
+            'B' => '7',
+            'C' => '8',
+            'D' => 'B',
+            _ => panic!("Bad current char")
+        },
+        'D' => match current {
+            'A'|'D'|'C'|'5'|'9' => current,
+            '1' => '3',
+            '2' => '6',
+            '3' => '7',
+            '4' => '8',
+            '6' => 'A',
+            '7' => 'B',
+            '8' => 'C',
+            'B' => 'D',
+            _ => panic!("Bad current char")
+        },
+        'L' => match current {
+            '1'|'2'|'5'|'A'|'D' => current,
+            '3' => '2',
+            '4' => '3',
+            '6' => '5',
+            '7' => '6',
+            '8' => '7',
+            '9' => '8',
+            'B' => 'A',
+            'C' => 'B',
+            _ => panic!("Bad current char")
+        },
+        'R' => match current {
+            '1'|'4'|'9'|'C'|'D' => current,
+            '2' => '3',
+            '3' => '4',
+            '5' => '6',
+            '6' => '7',
+            '7' => '8',
+            '8' => '9',
+            'A' => 'B',
+            'B' => 'C',
+            _ => panic!("Bad current char")
+        },
+        _ => panic!("Bad direction character")
+    }
+}