optimize p2
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2de9cca374
commit
515b47714d
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@ -1,5 +1,7 @@
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#![feature(test)]
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extern crate test;
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use std::collections::HashSet;
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use aoc2022::{
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boilerplate,
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common::*,
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@ -35,36 +37,33 @@ fn parse_input(raw: &str) -> Parsed {
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(start, end, grid)
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}
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/// This is like… O(n³) or something for grid size n :tehe:
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fn part1((start, end, grid): &Parsed) -> usize {
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let xbounds = 0..grid.len();
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let ybounds = 0..grid.fields[0].len();
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let mut distances = VecGrid { fields: vec![vec![usize::MAX; ybounds.end]; xbounds.end] };
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let mut visited = VecGrid { fields: vec![vec![false; ybounds.end]; xbounds.end] };
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let mut points_to_consider = HashSet::from([*start]);
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distances[*start] = 0;
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let mut curr = *start;
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loop {
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if &curr == end {
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return distances[curr];
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}
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points_to_consider.remove(&curr);
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for n in curr
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.neighbors_no_diagonals()
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.into_iter()
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.filter(|&PositionND([x, y])| xbounds.contains(&(x as usize)) && ybounds.contains(&(y as usize)))
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{
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if grid[curr] >= grid[n] || grid[n] - grid[curr] == 1 {
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distances[n] = distances[n].min(distances[curr] + 1);
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if !visited[n] {
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if grid[curr] >= grid[n] || grid[n] - grid[curr] == 1 {
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distances[n] = distances[n].min(distances[curr] + 1);
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}
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points_to_consider.insert(n);
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}
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}
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distances[curr] = usize::MAX;
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let min = distances.fields.iter().flatten().min().unwrap();
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curr = distances
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.fields
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.iter()
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.enumerate()
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.find_map(|(x, row)| {
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row.iter().enumerate().find_map(|(y, e)| (e == min).then_some(y)).map(|y| PositionND([x as i64, y as i64]))
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})
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.unwrap();
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visited[curr] = true;
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curr = *points_to_consider.iter().min_by_key(|&&p| distances[p]).unwrap();
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}
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}
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@ -72,31 +71,29 @@ fn part2((_, end, grid): &Parsed) -> usize {
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let xbounds = 0..grid.len();
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let ybounds = 0..grid.fields[0].len();
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let mut distances = VecGrid { fields: vec![vec![usize::MAX; ybounds.end]; xbounds.end] };
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let mut visited = VecGrid { fields: vec![vec![false; ybounds.end]; xbounds.end] };
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let mut points_to_consider = HashSet::from([*end]);
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distances[*end] = 0;
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let mut curr = *end;
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loop {
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if grid[curr] == b'a' {
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return distances[curr];
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}
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points_to_consider.remove(&curr);
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for n in curr
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.neighbors_no_diagonals()
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.into_iter()
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.filter(|&PositionND([x, y])| xbounds.contains(&(x as usize)) && ybounds.contains(&(y as usize)))
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{
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if grid[curr] <= grid[n] || grid[curr] - grid[n] == 1 {
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distances[n] = distances[n].min(distances[curr] + 1);
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if !visited[n] {
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if grid[curr] <= grid[n] || grid[curr] - grid[n] == 1 {
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distances[n] = distances[n].min(distances[curr] + 1);
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}
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points_to_consider.insert(n);
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}
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}
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distances[curr] = usize::MAX;
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let min = distances.fields.iter().flatten().min().unwrap();
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curr = distances
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.fields
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.iter()
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.enumerate()
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.find_map(|(x, row)| {
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row.iter().enumerate().find_map(|(y, e)| (e == min).then_some(y)).map(|y| PositionND([x as i64, y as i64]))
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})
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.unwrap();
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visited[curr] = true;
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curr = *points_to_consider.iter().min_by_key(|&&p| distances[p]).unwrap();
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}
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}
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