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Preallocate day 5 hashmaps

This commit is contained in:
kageru 2021-12-05 22:00:14 +01:00
parent 45600f5dd1
commit fcfb68ea33
Signed by: kageru
GPG Key ID: 8282A2BEA4ADA3D2
1 changed files with 6 additions and 5 deletions
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11
2021/src/bin/day05.rs
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@ -2,7 +2,8 @@
#![feature(test)]
extern crate test;
use aoc2021::common::*;
use fnv::FnvHashMap;
use fnv::{FnvHashMap, FnvHasher};
use std::hash::BuildHasherDefault;
const DAY: usize = 5;
type Coordinate = (i16, i16); // twice as fast as using i64s ¯\_(ツ)_/¯
@ -16,11 +17,11 @@ fn parse_input(raw: &str) -> Parsed {
.collect()
}
fn solve<F: FnMut(&(Coordinate, Coordinate)) -> Vec<Coordinate>>(parsed: &Parsed, f: F) -> usize {
fn solve<F: FnMut(&(Coordinate, Coordinate)) -> Vec<Coordinate>>(parsed: &Parsed, capacity: usize, f: F) -> usize {
parsed
.iter()
.flat_map(f)
.fold(FnvHashMap::default(), |mut map, c| {
.fold(FnvHashMap::with_capacity_and_hasher(capacity, BuildHasherDefault::<FnvHasher>::default()), |mut map, c| {
*map.entry(c).or_insert(0) += 1;
map
})
@ -30,7 +31,7 @@ fn solve<F: FnMut(&(Coordinate, Coordinate)) -> Vec<Coordinate>>(parsed: &Parsed
}
fn part1(parsed: &Parsed) -> usize {
solve(parsed, |&cs| match cs {
solve(parsed, parsed.len() * 200, |&cs| match cs {
((x1, y1), (x2, y2)) if x1 == x2 => (y1.min(y2)..=y1.max(y2)).map(|y| (x1, y)).collect(),
((x1, y1), (x2, y2)) if y1 == y2 => (x1.min(x2)..=x1.max(x2)).map(|x| (x, y1)).collect(),
_ => vec![],
@ -39,7 +40,7 @@ fn part1(parsed: &Parsed) -> usize {
fn part2(parsed: &Parsed) -> usize {
let offset = |x1, x2| (x1 < x2) as i16 - (x1 > x2) as i16;
solve(parsed, |&((mut x1, mut y1), (x2, y2))| {
solve(parsed, parsed.len() * 400, |&((mut x1, mut y1), (x2, y2))| {
let mut coords = Vec::with_capacity(x1.abs_diff(x2).max(y1.abs_diff(y2)) as usize + 1);
let x_offset = offset(x1, x2);
let y_offset = offset(y1, y2);