55 lines
1.3 KiB
Rust
55 lines
1.3 KiB
Rust
#![feature(test)]
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extern crate test;
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use std::collections::HashMap;
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type Parsed = Vec<usize>;
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fn read_input() -> String {
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String::from("15,12,0,14,3,1")
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}
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fn parse_input(raw: &str) -> Parsed {
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raw.split(',').filter_map(|x| x.parse().ok()).collect()
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}
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fn part1(parsed: &Parsed, limit: usize) -> usize {
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(parsed.len()..limit - 1)
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.fold(
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(parsed.iter().enumerate().map(|(i, n)| (*n, i)).collect::<HashMap<_, _>>(), 0),
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|(mut prev, curr), i| {
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let next = prev.get(&curr).map(|p| i - p).unwrap_or(0);
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prev.insert(curr, i);
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(prev, next)
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},
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)
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.1
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}
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// only here so the test/bench macro works
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#[inline]
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fn part2(parsed: &Parsed, limit: usize) -> usize {
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part1(parsed, limit)
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}
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fn main() {
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let input = parse_input(&read_input());
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println!("Part 1: {}", part1(&input, 2020));
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println!("Part 2: {}", part1(&input, 30000000));
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use aoc2020::*;
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use paste::paste;
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use test::black_box;
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const TEST_INPUT: &str = "0,3,6";
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test!(part1(2020) == 436);
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test!(part2(30000000) == 175594);
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bench!(part1(2020) == 249);
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// bench!(part2(30000000) == 41687);
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bench_input!(len == 6);
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}
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