Progress on day 12
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@ -36,20 +36,123 @@ impl Grid<char> {
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#[derive(Debug)]
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struct Pathfinder {
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current_elevation: char,
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current_idx: usize,
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start_idx: usize,
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end_idx: usize,
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grid: Grid<char>,
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steps: Vec<Direction>,
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}
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impl Pathfinder {
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pub fn from_file_str(file_str: &str) -> Self {
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Pathfinder {
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let mut pf = Pathfinder {
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current_elevation: 'a',
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current_idx: 0,
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start_idx: 0,
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end_idx: 0,
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grid: Grid::from_file_str(file_str),
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steps: Vec::new(),
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}
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};
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pf.go_to_start();
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pf
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}
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fn find_start_and_end(&self) -> (usize, usize) {
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(self.grid.find_pos('S').unwrap(), self.grid.find_pos('E').unwrap())
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(self.start_idx, self.end_idx)
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}
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fn go_to_start(&mut self) {
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let start = self.grid.find_pos('S').unwrap();
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let end = self.grid.find_pos('E').unwrap();
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self.current_idx = start;
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self.start_idx = start;
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self.end_idx = end;
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self.current_elevation = 'a';
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self.grid.vec[start] = 'a';
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self.grid.vec[end] = 'z';
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}
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fn get_index_for_move(&self, from: usize, dir: Direction) -> Option<usize> {
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let (mut x, mut y) = self.grid.idx_xy(from);
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match dir {
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Direction::Up => {
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if y >= 1 {
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y -= 1;
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} else {
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return None;
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}
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}
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Direction::Down => {
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if y < self.grid.num_rows() - 1 {
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y += 1;
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} else {
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return None;
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}
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}
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Direction::Left => {
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if x >= 1 {
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x -= 1;
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} else {
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return None;
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}
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}
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Direction::Right => {
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if x < self.grid.num_cols() - 1 {
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x += 1;
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} else {
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return None;
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}
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}
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};
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Some(self.grid.xy_idx(x, y))
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}
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fn is_valid_move(&self, start: usize, dir: Direction) -> bool {
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if let Some(end) = self.get_index_for_move(start, dir) {
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// Is the item within the grid?
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let start_char = self.grid.get(start);
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let end_char = self.grid.get(end);
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if start_char.is_none() || end_char.is_none() {
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return false;
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}
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// Is the elevation change 0 or 1?
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let start_char = *start_char.unwrap();
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let end_char = *end_char.unwrap();
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println!("start, end: {}, {}", start_char, end_char);
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let diff = end_char.to_digit(26).unwrap() - start_char.to_digit(26).unwrap();
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if diff > 1 || end_char < start_char {
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return false;
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}
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let (start_x, start_y) = self.grid.idx_xy(start);
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let (end_x, end_y) = self.grid.idx_xy(end);
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let x_diff = usize::abs_diff(end_x, start_x);
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let y_diff = usize::abs_diff(end_y, start_y);
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// Have we moved 0 or 1 in a cardinal direction?
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return match (x_diff, y_diff) {
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(0, 0) | (0, 1) | (1,0) => true,
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_ => false,
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};
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};
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false
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}
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fn find_valid_moves(&self, start: usize) -> Vec<usize> {
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[Direction::Up, Direction::Down, Direction::Left, Direction::Right]
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.into_iter()
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.filter(|d| self.is_valid_move(start, *d))
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.map(|d| self.get_index_for_move(start, d))
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.filter(|m| m.is_some())
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.map(|m| m.unwrap())
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.collect()
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}
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}
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@ -75,4 +178,13 @@ mod tests {
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assert_eq!((start, end), (0, 21));
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}
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#[test]
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fn find_valid_moves() {
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let finder = Pathfinder::from_file_str(get_test_data());
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let (start, end) = finder.find_start_and_end();
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assert_eq!(finder.find_valid_moves(start), vec![8, 1]);
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assert_eq!(finder.find_valid_moves(8), vec![16, 9]);
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}
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}
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