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use std::char;
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pub fn solve(input: &str) -> String {
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let arrangement = vec![
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vec![None, None, Some('1'), None, None],
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vec![None, Some('2'), Some('3'), Some('4'), None],
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vec![Some('5'), Some('6'), Some('7'), Some('8'), Some('9')],
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vec![None, Some('A'), Some('B'), Some('C'), None],
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vec![None, None, Some('D'), None, None],
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];
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let mut keypad = Keypad {
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arrangement: arrangement,
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current: (0, 2),
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};
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let mut answer = String::new();
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for c in input.chars() {
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match c {
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'U' => {
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keypad.move_(Dir::Up);
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}
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'D' => {
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keypad.move_(Dir::Down);
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}
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'L' => {
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keypad.move_(Dir::Left);
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}
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'R' => {
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keypad.move_(Dir::Right);
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}
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'\n' => {
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answer.push(keypad.button());
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}
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_ => {
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unreachable!();
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}
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}
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}
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answer.push(keypad.button());
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answer
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}
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#[test]
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fn test_solve() {
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let instructions = "ULL
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RRDDD
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LURDL
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UUUUD";
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assert_eq!(solve(instructions), "5DB3".to_string());
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}
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struct Keypad {
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arrangement: Vec<Vec<Option<char>>>,
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current: (usize, usize),
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}
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impl Keypad {
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fn move_(&mut self, dir: Dir) {
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let (dx, dy): (isize, isize) = match dir {
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Dir::Up => (0, -1),
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Dir::Down => (0, 1),
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Dir::Left => (-1, 0),
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Dir::Right => (1, 0),
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};
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let x = (self.current.0 as isize + dx) as usize;
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let y = (self.current.1 as isize + dy) as usize;
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if self.button_at(x, y).is_some() {
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self.current = (x, y);
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}
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}
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fn button(&self) -> char {
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let (x, y) = self.current;
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self.arrangement[y][x].unwrap()
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}
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fn button_at(&self, x: usize, y: usize) -> Option<char> {
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self.arrangement.get(y).and_then(|row| row.get(x).and_then(|c| *c))
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}
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}
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enum Dir {
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Up,
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Down,
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Left,
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Right,
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}
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#[test]
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fn test_keypad() {
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let arrangement = vec![
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vec!['1', '2', '3'],
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vec!['4', '5', '6'],
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vec!['7', '8', '9'],
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]
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.iter()
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.map(|row| row.iter().map(|x| Some(*x)).collect())
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.collect();
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let mut keypad = Keypad {
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arrangement: arrangement,
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current: (1, 1),
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};
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assert_eq!(keypad.button_at(1, 1), Some('5'));
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assert_eq!(keypad.button(), '5');
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keypad.move_(Dir::Up);
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assert_eq!(keypad.button(), '2');
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keypad.move_(Dir::Up);
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assert_eq!(keypad.button(), '2');
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}
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