optimize p2

This commit is contained in:
kageru 2022-12-12 17:19:53 +01:00
parent 2de9cca374
commit 515b47714d

View File

@ -1,5 +1,7 @@
#![feature(test)]
extern crate test;
use std::collections::HashSet;
use aoc2022::{
boilerplate,
common::*,
@ -35,36 +37,33 @@ fn parse_input(raw: &str) -> Parsed {
(start, end, grid)
}
/// This is like… O(n³) or something for grid size n :tehe:
fn part1((start, end, grid): &Parsed) -> usize {
let xbounds = 0..grid.len();
let ybounds = 0..grid.fields[0].len();
let mut distances = VecGrid { fields: vec![vec![usize::MAX; ybounds.end]; xbounds.end] };
let mut visited = VecGrid { fields: vec![vec![false; ybounds.end]; xbounds.end] };
let mut points_to_consider = HashSet::from([*start]);
distances[*start] = 0;
let mut curr = *start;
loop {
if &curr == end {
return distances[curr];
}
points_to_consider.remove(&curr);
for n in curr
.neighbors_no_diagonals()
.into_iter()
.filter(|&PositionND([x, y])| xbounds.contains(&(x as usize)) && ybounds.contains(&(y as usize)))
{
if grid[curr] >= grid[n] || grid[n] - grid[curr] == 1 {
distances[n] = distances[n].min(distances[curr] + 1);
if !visited[n] {
if grid[curr] >= grid[n] || grid[n] - grid[curr] == 1 {
distances[n] = distances[n].min(distances[curr] + 1);
}
points_to_consider.insert(n);
}
}
distances[curr] = usize::MAX;
let min = distances.fields.iter().flatten().min().unwrap();
curr = distances
.fields
.iter()
.enumerate()
.find_map(|(x, row)| {
row.iter().enumerate().find_map(|(y, e)| (e == min).then_some(y)).map(|y| PositionND([x as i64, y as i64]))
})
.unwrap();
visited[curr] = true;
curr = *points_to_consider.iter().min_by_key(|&&p| distances[p]).unwrap();
}
}
@ -72,31 +71,29 @@ fn part2((_, end, grid): &Parsed) -> usize {
let xbounds = 0..grid.len();
let ybounds = 0..grid.fields[0].len();
let mut distances = VecGrid { fields: vec![vec![usize::MAX; ybounds.end]; xbounds.end] };
let mut visited = VecGrid { fields: vec![vec![false; ybounds.end]; xbounds.end] };
let mut points_to_consider = HashSet::from([*end]);
distances[*end] = 0;
let mut curr = *end;
loop {
if grid[curr] == b'a' {
return distances[curr];
}
points_to_consider.remove(&curr);
for n in curr
.neighbors_no_diagonals()
.into_iter()
.filter(|&PositionND([x, y])| xbounds.contains(&(x as usize)) && ybounds.contains(&(y as usize)))
{
if grid[curr] <= grid[n] || grid[curr] - grid[n] == 1 {
distances[n] = distances[n].min(distances[curr] + 1);
if !visited[n] {
if grid[curr] <= grid[n] || grid[curr] - grid[n] == 1 {
distances[n] = distances[n].min(distances[curr] + 1);
}
points_to_consider.insert(n);
}
}
distances[curr] = usize::MAX;
let min = distances.fields.iter().flatten().min().unwrap();
curr = distances
.fields
.iter()
.enumerate()
.find_map(|(x, row)| {
row.iter().enumerate().find_map(|(y, e)| (e == min).then_some(y)).map(|y| PositionND([x as i64, y as i64]))
})
.unwrap();
visited[curr] = true;
curr = *points_to_consider.iter().min_by_key(|&&p| distances[p]).unwrap();
}
}