61 lines
1.4 KiB
Rust
61 lines
1.4 KiB
Rust
#![feature(test, bool_to_option)]
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extern crate test;
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use itertools::Itertools;
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use std::env;
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fn read_input() -> Vec<usize> {
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std::fs::read_to_string(
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env::args()
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.nth(1)
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.filter(|n| n != "--bench")
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.unwrap_or_else(|| String::from("inputs/day01")),
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)
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.unwrap()
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.lines()
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.filter_map(|l| l.parse().ok())
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.collect()
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}
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fn part1(input: &[usize]) -> usize {
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input
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.iter()
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.tuple_combinations()
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.find_map(|(&a, &b)| (a + b == 2020).then_some(a * b))
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.unwrap()
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}
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fn part2(input: &[usize]) -> usize {
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let mut p2_table = [None; 2020];
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for (&a, &b) in input.iter().tuple_combinations() {
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if a + b < 2020 {
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p2_table[a + b] = Some((a, b))
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}
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}
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let (a, b) = input.iter().find_map(|x| p2_table[2020 - x]).unwrap();
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a * b * (2020 - a - b)
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}
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fn main() {
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let input = read_input();
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println!("Part 1: {}", part1(&input));
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println!("Part 2: {}", part2(&input));
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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 test::{black_box, Bencher};
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#[bench]
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fn bench_part1(b: &mut Bencher) {
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let input = read_input();
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b.iter(|| black_box(part1(black_box(&input))));
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}
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#[bench]
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fn bench_part2(b: &mut Bencher) {
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let input = read_input();
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b.iter(|| black_box(part2(black_box(&input))));
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}
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}
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