366 lines
9.3 KiB
Rust
366 lines
9.3 KiB
Rust
use std::collections::HashSet;
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#[derive(Debug, Copy, Clone, PartialOrd, PartialEq, Eq, Hash)]
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enum VisibleDirection {
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Top,
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Bottom,
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Left,
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Right,
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}
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use VisibleDirection::*;
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#[derive(Debug, Default)]
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struct Tree {
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height: usize,
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visible: HashSet<VisibleDirection>,
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}
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impl Tree {
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fn new(height: usize) -> Self {
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Tree {
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height,
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..Tree::default()
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}
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}
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fn is_visible(&self) -> bool {
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!self.visible.is_empty()
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}
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fn set_visible(&mut self, dir: VisibleDirection) -> &mut Self {
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self.visible.insert(dir);
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self
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}
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fn set_all_visible(&mut self) -> &mut Self {
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self.set_visible(Top)
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.set_visible(Bottom)
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.set_visible(Left)
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.set_visible(Right)
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}
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}
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// ----------------------------------------------------------------------------
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#[derive(Debug)]
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struct Grid<T> {
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width: usize,
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vec: Vec<T>,
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}
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impl<T> Grid<T> {
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pub fn new(width: usize) -> Self {
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Grid {
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width,
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vec: Vec::new(),
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}
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}
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// Convert x,y coordinate into linear array index
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pub fn xy_idx(&self, x: usize, y: usize) -> usize {
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(y * self.width) + x
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}
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/// Convert linear array index to x,y coordinate
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pub fn idx_xy(&self, idx: usize) -> (usize, usize) {
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(idx % self.width, idx / self.width)
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}
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pub fn get(&self, idx: usize) -> Option<&T> {
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self.vec.get(idx)
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}
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pub fn get_mut(&mut self, idx: usize) -> Option<&mut T> {
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self.vec.get_mut(idx)
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}
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pub fn get_xy(&self, x: usize, y: usize) -> Option<&T> {
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self.get(self.xy_idx(x, y))
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}
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pub fn get_xy_mut(&mut self, x: usize, y: usize) -> Option<&mut T> {
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self.get_mut(self.xy_idx(x, y))
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}
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pub fn row_first_idx(&self, row: usize) -> usize {
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let idx = row * self.width;
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if idx < self.vec.len() {
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idx
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} else {
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self.vec.len()
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}
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}
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pub fn row_last_idx(&self, row: usize) -> usize {
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if (row + 1) > self.num_rows() {
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return self.vec.len();
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}
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self.row_first_idx(row + 1) - 1
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}
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pub fn num_rows(&self) -> usize {
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self.vec.len() / self.width
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}
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pub fn num_cols(&self) -> usize {
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self.width
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}
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pub fn get_row(&mut self, row_num: usize) -> &mut [T] {
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let start = self.row_first_idx(row_num);
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let end = self.row_last_idx(row_num);
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&mut self.vec[start..=end]
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}
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pub fn get_row_indexes(&self, row_num: usize) -> Vec<usize> {
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let start = self.row_first_idx(row_num);
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let end = self.row_last_idx(row_num);
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(start..=end).collect()
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}
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pub fn get_column_indexes(&self, col_num: usize) -> Vec<usize> {
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let mut indexes = Vec::new();
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if col_num >= self.num_cols() {
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panic!(
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"Asked for column {}, there are {} columns",
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col_num,
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self.num_cols()
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);
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}
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for r in 0..self.num_rows() {
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let idx = self.width * r + col_num;
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indexes.push(idx);
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}
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indexes
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}
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}
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impl Grid<Tree> {
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pub fn from_file_str(file_str: &'static str) -> Grid<Tree> {
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let lines: Vec<&str> = file_str.lines().collect();
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let width = lines[0].len();
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let mut grid: Grid<Tree> = Grid::new(width);
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for line in lines {
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let mut row: Vec<Tree> = line
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.chars()
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.map(|ch| Tree::new(ch.to_digit(10).unwrap() as usize))
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.collect();
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grid.vec.append(&mut row);
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}
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grid
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}
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fn mark_outer_trees_visible(&mut self) -> &mut Self {
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fn set_row_visible(row: &mut [Tree]) {
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row.iter_mut().for_each(|tree| {
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tree.set_all_visible();
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})
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}
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// Set top/bottom rows as visible
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set_row_visible(self.get_row(0));
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set_row_visible(self.get_row(self.num_rows() - 1));
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// Set left/right cols as visible
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self.get_column_indexes(0).into_iter().for_each(|id| {
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self.vec[id].set_all_visible();
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});
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self.get_column_indexes(self.num_cols() - 1)
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.into_iter()
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.for_each(|id| {
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self.vec[id].set_all_visible();
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});
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self
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}
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fn mark_visible(&mut self, dir: VisibleDirection) -> &mut Self {
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let indexes: Vec<Vec<usize>> = match dir {
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Top | Bottom => {
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// Skip outer columns, as those are already marked visible
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(1..(self.num_cols() - 1))
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.map(|c| self.get_column_indexes(c))
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.map(|column| {
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if dir == Bottom {
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column.into_iter().rev().collect()
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} else {
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column
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}
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})
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.collect()
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}
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Left | Right => {
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// Skip first and last rows, as those are already marked visible
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(1..(self.num_rows() - 1))
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.map(|r| self.get_row_indexes(r))
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.map(|row| {
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if dir == Right {
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row.into_iter().rev().collect()
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} else {
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row
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}
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})
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.collect()
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}
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};
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for row_or_col in indexes {
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let mut tallest = 0usize;
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for idx in row_or_col {
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let tree = self.get_mut(idx).unwrap();
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if tallest < tree.height {
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tree.set_visible(dir);
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tallest = tree.height;
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}
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}
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}
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self
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}
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pub fn mark_visible_trees(&mut self) {
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self.mark_outer_trees_visible()
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.mark_visible(Top)
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.mark_visible(Right)
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.mark_visible(Bottom)
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.mark_visible(Left);
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}
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pub fn get_visible_trees(&self) -> usize {
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self.vec
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.iter()
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.filter(|tree| tree.is_visible())
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.collect::<Vec<&Tree>>()
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.len()
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}
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fn get_surrounding_trees(&self, reference: usize) -> (Vec<usize>, Vec<usize>, Vec<usize>, Vec<usize>) {
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let (x, y) = self.idx_xy(reference);
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let mut top = self.get_column_indexes(x); // col[0..=x]
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let bottom = top.split_off(y + 1); // col[(x+1)..]
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let mut left = self.get_row_indexes(y); // row[0..=y]
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let right = left.split_off(x + 1); // row[(y+1)..]
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// Remove the index for the current tree
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let _ = top.pop();
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let _ = left.pop();
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// Reverse the top and left so the perspective is from the reference
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top.reverse();
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left.reverse();
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(top, right, bottom, left)
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}
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fn get_viewing_distance(&mut self, reference: usize) -> (usize, usize, usize, usize) {
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let (t, r, b, l) = self.get_surrounding_trees(reference);
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todo!();
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}
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}
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// ----------------------------------------------------------------------------
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fn main() {
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let file_str = include_str!("input.txt");
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let mut grid = Grid::from_file_str(file_str);
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grid.mark_visible_trees();
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let visible_num = grid.get_visible_trees();
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println!("Part 1: Number of visible trees: {}", visible_num);
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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fn get_data() -> &'static str {
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include_str!("test-input.txt")
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}
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#[test]
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fn test_row_first_index() {
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let grid = Grid::from_file_str(get_data());
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assert_eq!(grid.row_first_idx(1), 5);
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assert_eq!(grid.row_first_idx(0), 0);
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assert_eq!(grid.row_first_idx(2), 10);
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}
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#[test]
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fn test_row_last_index() {
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let grid = Grid::from_file_str(get_data());
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assert_eq!(grid.row_last_idx(0), 4);
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assert_eq!(grid.row_last_idx(1), 9);
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}
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#[test]
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fn test_get_column_indexes() {
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let grid = Grid::from_file_str(get_data());
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assert_eq!(grid.width, 5);
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assert_eq!(grid.get_column_indexes(0), vec![0, 5, 10, 15, 20]);
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assert_eq!(grid.get_column_indexes(1), vec![1, 6, 11, 16, 21]);
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assert_eq!(grid.get_column_indexes(4), vec![4, 9, 14, 19, 24]);
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}
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#[test]
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fn test_outer_visible_trees() {
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let mut grid = Grid::from_file_str(get_data());
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grid.mark_outer_trees_visible();
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assert_eq!(grid.get_visible_trees(), 16usize);
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}
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#[test]
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fn test_visible_trees() {
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let mut grid = Grid::from_file_str(get_data());
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grid.mark_visible_trees();
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let visible = [(1usize, 1usize), (2, 1), (1, 2), (4, 3), (2, 3)];
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for (x, y) in visible {
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let idx = grid.xy_idx(x, y);
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assert!(
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grid.vec[idx].is_visible(),
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"Tree {}({},{}) should be visible: {:#?}",
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idx,
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x,
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y,
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grid.vec[idx]
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);
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}
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assert_eq!(grid.get_visible_trees(), 21usize);
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}
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#[test]
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fn test_get_surrounding_trees() {
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let grid = Grid::from_file_str(get_data());
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let (t, r, b, l) = grid.get_surrounding_trees(7);
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assert_eq!(t, vec![2]);
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assert_eq!(r, vec![8, 9]);
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assert_eq!(b, vec![12, 17, 22]);
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assert_eq!(l, vec![6, 5]);
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}
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}
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