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Diffstat (limited to 'day08b/src/main.rs')
| -rw-r--r-- | day08b/src/main.rs | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/day08b/src/main.rs b/day08b/src/main.rs new file mode 100644 index 0000000..c9d3a52 --- /dev/null +++ b/day08b/src/main.rs @@ -0,0 +1,120 @@ +/// --- Part Two --- +/// +/// Content with the amount of tree cover available, the Elves just need to know the best spot to +/// build their tree house: they would like to be able to see a lot of trees. +/// +/// To measure the viewing distance from a given tree, look up, down, left, and right from that +/// tree; stop if you reach an edge or at the first tree that is the same height or taller than the +/// tree under consideration. (If a tree is right on the edge, at least one of its viewing +/// distances will be zero.) +/// +/// The Elves don't care about distant trees taller than those found by the rules above; the +/// proposed tree house has large eaves to keep it dry, so they wouldn't be able to see higher than +/// the tree house anyway. +/// +/// In the example above, consider the middle 5 in the second row: +/// +/// ``` +/// 30373 +/// 25512 +/// 65332 +/// 33549 +/// 35390 +/// ``` +/// +/// Looking up, its view is not blocked; it can see 1 tree (of height 3). +/// Looking left, its view is blocked immediately; it can see only 1 tree (of height 5, right +/// next to it). +/// Looking right, its view is not blocked; it can see 2 trees. +/// Looking down, its view is blocked eventually; it can see 2 trees (one of height 3, then the +/// tree of height 5 that blocks its view). +/// +/// A tree's scenic score is found by multiplying together its viewing distance in each of the four +/// directions. For this tree, this is 4 (found by multiplying 1 * 1 * 2 * 2). +/// +/// However, you can do even better: consider the tree of height 5 in the middle of the fourth row: +/// +/// ``` +/// 30373 +/// 25512 +/// 65332 +/// 33549 +/// 35390 +/// ``` +/// +/// Looking up, its view is blocked at 2 trees (by another tree with a height of 5). +/// Looking left, its view is not blocked; it can see 2 trees. +/// Looking down, its view is also not blocked; it can see 1 tree. +/// Looking right, its view is blocked at 2 trees (by a massive tree of height 9). +/// +/// This tree's scenic score is 8 (2 * 2 * 1 * 2); this is the ideal spot for the tree house. +/// +/// Consider each tree on your map. What is the highest scenic score possible for any tree? +use clap::Parser; +use itertools::Itertools; + +use std::fs::File; +use std::io::prelude::*; +use std::io::BufReader; +use std::path::PathBuf; + +const FILEPATH: &'static str = "examples/input.txt"; + +#[derive(Parser, Debug)] +#[clap(author, version, about, long_about = None)] +struct Cli { + #[clap(short, long, default_value = FILEPATH)] + file: PathBuf, +} + +fn main() { + let args = Cli::parse(); + + let file = File::open(&args.file).unwrap(); + let reader = BufReader::new(file); + let grid = reader + .lines() + .map(|l| { + l.unwrap() + .chars() + .map(|c| c.to_digit(10).unwrap() as u8) + .collect_vec() + }) + .collect_vec(); + + let xdim = grid.len(); + let ydim = grid[0].len(); + + let res = (1..(xdim - 1)) + .cartesian_product(1..(ydim - 1)) + .map(|(idx, idy)| { + let tree = grid[idx][idy]; + let top = (0..idx) + .rev() + .map(|t| tree as i32 - grid[t][idy] as i32) + .position(|diff| diff <= 0) + .unwrap_or(idx - 1) + + 1; + let bottom = ((idx + 1)..xdim) + .map(|t| tree as i32 - grid[t][idy] as i32) + .position(|diff| diff <= 0) + .unwrap_or((xdim - idx) - 2) + + 1; + let left = (0..idy) + .rev() + .map(|t| tree as i32 - grid[idx][t] as i32) + .position(|diff| diff <= 0) + .unwrap_or(idy - 1) + + 1; + let right = ((idy + 1)..ydim) + .map(|t| tree as i32 - grid[idx][t] as i32) + .position(|diff| diff <= 0) + .unwrap_or((ydim - idy) - 2) + + 1; + top * bottom * left * right + }) + .max() + .unwrap(); + + println!("{res:?}"); +} |