2020: day13: part 1

This commit is contained in:
Antoine Martin 2020-12-13 15:22:23 +01:00
parent bae2c9cb2c
commit 39d7098f36
6 changed files with 73 additions and 0 deletions

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@ -12,6 +12,7 @@ use aoc2020::day09;
use aoc2020::day10;
use aoc2020::day11;
use aoc2020::day12;
use aoc2020::day13;
fn aoc2020_all(c: &mut Criterion) {
c.bench_function("day01", |b| b.iter(|| day01::run().unwrap()));
@ -26,6 +27,7 @@ fn aoc2020_all(c: &mut Criterion) {
c.bench_function("day10", |b| b.iter(|| day10::run().unwrap()));
c.bench_function("day11", |b| b.iter(|| day11::run().unwrap()));
c.bench_function("day12", |b| b.iter(|| day12::run().unwrap()));
c.bench_function("day13", |b| b.iter(|| day13::run().unwrap()));
}
criterion_group! {

2
aoc2020/input/day13.txt Normal file
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@ -0,0 +1,2 @@
1008713
13,x,x,41,x,x,x,x,x,x,x,x,x,467,x,x,x,x,x,x,x,x,x,x,x,19,x,x,x,x,17,x,x,x,x,x,x,x,x,x,x,x,29,x,353,x,x,x,x,x,37,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,23

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@ -0,0 +1,2 @@
939
7,13,x,x,59,x,31,19

64
aoc2020/src/day13.rs Normal file
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@ -0,0 +1,64 @@
use std::fmt::Write;
use aoc::err;
const INPUT: &str = include_str!("../input/day13.txt");
pub fn run() -> aoc::Result<String> {
let mut res = String::with_capacity(128);
writeln!(res, "part 1: {}", part1(INPUT)?)?;
Ok(res)
}
fn part1(input: &str) -> aoc::Result<u64> {
let mut lines = input.lines();
let earliest_timestamp = lines
.next()
.ok_or_else(|| err!("input was empty"))?
.parse::<u64>()
.map_err(|e| err!("couldn't parse first line: {}", e))?;
let bus_ids = lines
.next()
.ok_or_else(|| err!("no second line"))?
.split(',')
.filter_map(|num| {
if num == "x" {
None
} else {
Some(num.parse::<u64>().map_err(|e| err!("{}", e)))
}
})
.collect::<aoc::Result<Vec<_>>>()?;
let (bus_id, earliest_departure) = bus_ids
.iter()
.map(|id| {
let next_departure = ((earliest_timestamp / id) * id) + id;
(id, next_departure)
})
.min_by_key(|(_, next_departure)| *next_departure)
.unwrap();
Ok(bus_id * (earliest_departure - earliest_timestamp))
}
#[cfg(test)]
mod tests {
use super::*;
const PROVIDED: &str = include_str!("../input/day13_provided.txt");
#[test]
fn part1_provided() {
assert_eq!(part1(PROVIDED).unwrap(), 295);
}
#[test]
fn part1_real() {
assert_eq!(part1(INPUT).unwrap(), 3269);
}
}

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@ -10,3 +10,4 @@ pub mod day09;
pub mod day10;
pub mod day11;
pub mod day12;
pub mod day13;

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@ -13,6 +13,7 @@ use aoc2020::day09;
use aoc2020::day10;
use aoc2020::day11;
use aoc2020::day12;
use aoc2020::day13;
fn main() -> Result<()> {
let days: &[DayFunc] = &[
@ -28,6 +29,7 @@ fn main() -> Result<()> {
day10::run,
day11::run,
day12::run,
day13::run,
];
aoc::run(days)