Lots of progress on day 8 part 1

This commit is contained in:
Timothy Warren 2022-12-08 16:01:22 -05:00
parent aced557148
commit fcae876701
3 changed files with 211 additions and 11 deletions

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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. 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.
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. 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.
The Elves have already launched a quadcopter to generate a map with the height of each tree (your puzzle input). For example: The Elves have already launched a quadcopter to generate a map with the height of each tree (your puzzle input). For example:
@ -16,18 +16,18 @@ The Elves have already launched a quadcopter to generate a map with the height o
Each tree is represented as a single digit whose value is its height, where 0 is the shortest and 9 is the tallest. Each tree is represented as a single digit whose value is its height, where 0 is the shortest and 9 is the tallest.
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. 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.
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: 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:
* 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.) * 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.)
* The top-middle 5 is visible from the top and right. * The top-middle 5 is **visible** from the top and right.
* 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. * 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.
* The left-middle 5 is visible, but only from the right. * The left-middle 5 is **visible**, but only from the right.
* 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. * 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.
* The right-middle 3 is visible from the right. * The right-middle 3 is **visible** from the right.
* In the bottom row, the middle 5 is visible, but the 3 and 4 are not. * In the bottom row, the middle 5 is **visible**, but the 3 and 4 are not.
With 16 trees visible on the edge and another 5 visible in the interior, a total of 21 trees are visible in this arrangement. With 16 trees visible on the edge and another 5 visible in the interior, a total of 21 trees are visible in this arrangement.
Consider your map; how many trees are visible from outside the grid? **Consider your map; how many trees are visible from outside the grid?**

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use std::collections::HashSet;
#[derive(Debug, Copy, Clone, PartialOrd, PartialEq, Eq, Hash)]
enum VisibleDirection {
Top,
Bottom,
Left,
Right,
}
use VisibleDirection::*;
#[derive(Debug, Default)]
struct Tree {
height: usize,
visible: HashSet<VisibleDirection>,
}
impl Tree {
fn new(height: usize) -> Self {
Tree {
height,
..Tree::default()
}
}
fn is_visible(&self) -> bool {
!self.visible.is_empty()
}
fn set_visible(&mut self, dir: VisibleDirection) -> &mut Self {
self.visible.insert(dir);
self
}
fn set_all_visible(&mut self) -> &mut Self {
self.set_visible(Top)
.set_visible(Bottom)
.set_visible(Left)
.set_visible(Right)
}
}
// ----------------------------------------------------------------------------
#[derive(Debug)]
struct Grid<T> {
width: usize,
vec: Vec<T>,
}
impl<T> Grid<T> {
fn new(width: usize) -> Self {
Grid {
width,
vec: Vec::new(),
}
}
// Convert x,y coordinate into linear array index
fn xy_idx(&self, x: usize, y: usize) -> usize {
(y * self.width) + x
}
/// Convert linear array index to x,y coordinate
fn idx_xy(&self, idx: usize) -> (usize, usize) {
(idx % self.width, idx / self.width)
}
fn row_first_idx(&self, row: usize) -> usize {
let idx = row * self.width;
if idx < self.vec.len() {
idx
} else {
self.vec.len()
}
}
fn row_last_idx(&self, row: usize) -> usize {
if (row + 1) > self.num_rows() {
return self.vec.len();
}
self.row_first_idx(row + 1) - 1
}
fn num_rows(&self) -> usize {
let even_rows = self.vec.len() / self.width;
if self.vec.len() % self.width > 0 {
even_rows + 1
} else {
even_rows
}
}
fn num_cols(&self) -> usize {
self.width
}
fn get_row(&mut self, row_num: usize) -> &mut [T] {
let start = self.row_first_idx(row_num);
let end = self.row_last_idx(row_num);
&mut self.vec[start..=end]
}
fn get_column_indexes(&self, col_num: usize) -> Vec<usize> {
let mut indexes = Vec::new();
if col_num > self.num_cols() {
return indexes;
}
for r in 0..self.num_rows() {
let idx = self.width * r + col_num;
indexes.push(idx);
}
indexes
}
}
impl Grid<Tree> {
fn mark_outer_trees_visible(&mut self) {
fn set_row_visible(row: &mut [Tree]) {
row.iter_mut().for_each(|tree| { tree.set_all_visible(); })
}
// Set top/bottom rows as visible
set_row_visible(self.get_row(0));
set_row_visible(self.get_row(self.num_rows() - 1));
// Set left/right cols as visible
self.get_column_indexes(0).into_iter().for_each(|id| {
self.vec[id].set_all_visible();
});
self.get_column_indexes(self.num_cols() - 1).into_iter().for_each(|id| {
self.vec[id].set_all_visible();
});
}
fn mark_visible_trees(&mut self) {
self.mark_outer_trees_visible();
}
pub fn get_visible_trees(&self) -> usize {
self
.vec
.iter()
.filter(|tree| tree.is_visible())
.collect::<Vec<&Tree>>()
.len()
}
fn from_file_str(file_str: &'static str) -> Grid<Tree> {
let lines: Vec<&str> = file_str.lines().collect();
let width = lines[0].len();
let mut grid: Grid<Tree> = Grid::new(width);
for line in lines {
let mut row: Vec<Tree> = line
.chars()
.map(|ch| Tree::new(ch.to_digit(10).unwrap() as usize))
.collect();
grid.vec.append(&mut row);
}
grid
}
}
// ----------------------------------------------------------------------------
fn main() { fn main() {
let file_str = include_str!("input.txt"); let file_str = include_str!("input.txt");
let mut grid = Grid::from_file_str(file_str);
grid.mark_visible_trees();
let visible_num = grid.get_visible_trees();
println!("Part 1: Number of visible trees: {}", visible_num);
} }
#[cfg(test)] #[cfg(test)]
mod tests { mod tests {
use super::*; use super::*;
fn get_data() -> &'static str {
include_str!("test-input.txt")
}
#[test]
fn test_outer_visible_trees() {
let mut grid = Grid::from_file_str(get_data());
grid.mark_outer_trees_visible();
assert_eq!(grid.get_visible_trees(), 16usize);
}
} }

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day8/src/test-input.txt Normal file
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30373
25512
65332
33549
35390