Lots of progress on day 8 part 1
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The expedition comes across a peculiar patch of tall trees all planted carefully in a grid. The Elves explain that a previous expedition planted these trees as a reforestation effort. Now, they're curious if this would be a good location for a tree house.
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The expedition comes across a peculiar patch of tall trees all planted carefully in a grid. The Elves explain that a previous expedition planted these trees as a reforestation effort. Now, they're curious if this would be a good location for a tree house.
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First, determine whether there is enough tree cover here to keep a tree house hidden. To do this, you need to count the number of trees that are visible from outside the grid when looking directly along a row or column.
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First, determine whether there is enough tree cover here to keep a tree house **hidden**. To do this, you need to count the number of trees that are **visible from outside the grid** when looking directly along a row or column.
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The Elves have already launched a quadcopter to generate a map with the height of each tree (your puzzle input). For example:
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The Elves have already launched a quadcopter to generate a map with the height of each tree (your puzzle input). For example:
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@ -16,18 +16,18 @@ The Elves have already launched a quadcopter to generate a map with the height o
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Each tree is represented as a single digit whose value is its height, where 0 is the shortest and 9 is the tallest.
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Each tree is represented as a single digit whose value is its height, where 0 is the shortest and 9 is the tallest.
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A tree is visible if all of the other trees between it and an edge of the grid are shorter than it. Only consider trees in the same row or column; that is, only look up, down, left, or right from any given tree.
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A tree is **visible** if all of the other trees between it and an edge of the grid are **shorter** than it. Only consider trees in the same row or column; that is, only look up, down, left, or right from any given tree.
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All of the trees around the edge of the grid are visible - since they are already on the edge, there are no trees to block the view. In this example, that only leaves the interior nine trees to consider:
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All of the trees around the edge of the grid are **visible** - since they are already on the edge, there are no trees to block the view. In this example, that only leaves the **interior nine trees** to consider:
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* The top-left 5 is visible from the left and top. (It isn't visible from the right or bottom since other trees of height 5 are in the way.)
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* The top-left 5 is **visible** from the left and top. (It isn't visible from the right or bottom since other trees of height 5 are in the way.)
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* The top-middle 5 is visible from the top and right.
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* The top-middle 5 is **visible** from the top and right.
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* The top-right 1 is not visible from any direction; for it to be visible, there would need to only be trees of height 0 between it and an edge.
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* The top-right 1 is not visible from any direction; for it to be visible, there would need to only be trees of height **0** between it and an edge.
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* The left-middle 5 is visible, but only from the right.
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* The left-middle 5 is **visible**, but only from the right.
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* The center 3 is not visible from any direction; for it to be visible, there would need to be only trees of at most height 2 between it and an edge.
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* The center 3 is not visible from any direction; for it to be visible, there would need to be only trees of at most height 2 between it and an edge.
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* The right-middle 3 is visible from the right.
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* The right-middle 3 is **visible** from the right.
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* In the bottom row, the middle 5 is visible, but the 3 and 4 are not.
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* In the bottom row, the middle 5 is **visible**, but the 3 and 4 are not.
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With 16 trees visible on the edge and another 5 visible in the interior, a total of 21 trees are visible in this arrangement.
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With 16 trees visible on the edge and another 5 visible in the interior, a total of 21 trees are visible in this arrangement.
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Consider your map; how many trees are visible from outside the grid?
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**Consider your map; how many trees are visible from outside the grid?**
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195
day8/src/main.rs
195
day8/src/main.rs
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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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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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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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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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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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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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fn num_rows(&self) -> usize {
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let even_rows = self.vec.len() / self.width;
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if self.vec.len() % self.width > 0 {
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even_rows + 1
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} else {
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even_rows
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}
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}
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fn num_cols(&self) -> usize {
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self.width
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}
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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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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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return indexes;
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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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fn mark_outer_trees_visible(&mut self) {
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fn set_row_visible(row: &mut [Tree]) {
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row.iter_mut().for_each(|tree| { tree.set_all_visible(); })
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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).into_iter().for_each(|id| {
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self.vec[id].set_all_visible();
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});
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}
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fn mark_visible_trees(&mut self) {
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self.mark_outer_trees_visible();
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}
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pub fn get_visible_trees(&self) -> usize {
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self
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.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 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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}
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// ----------------------------------------------------------------------------
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fn main() {
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fn main() {
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let file_str = include_str!("input.txt");
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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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}
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#[cfg(test)]
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#[cfg(test)]
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mod tests {
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mod tests {
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use super::*;
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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_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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}
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}
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5
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30373
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35390
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Block a user