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use anyhow::Context as _;
use std::io::BufRead as _;
pub fn run(day: u8, puzzle: u8) -> anyhow::Result<()> {
match (day, puzzle) {
(1, 1) => report_repair(),
(1, 2) => report_repair_2(),
_ => Err(anyhow::anyhow!("unknown puzzle {}-{}", day, puzzle)),
}
}
fn report_repair() -> anyhow::Result<()> {
let ints = read_ints("data/1.txt")?;
for i in &ints {
for j in &ints {
if i + j == 2020 {
println!("{} * {} = {}", i, j, i * j);
return Ok(());
}
}
}
Err(anyhow::anyhow!("no numbers summing to 2020 found"))
}
fn report_repair_2() -> anyhow::Result<()> {
let ints = read_ints("data/1.txt")?;
for i in &ints {
for j in &ints {
for k in &ints {
if i + j + k == 2020 {
println!("{} * {} * {} = {}", i, j, k, i * j * k);
return Ok(());
}
}
}
}
Err(anyhow::anyhow!("no numbers summing to 2020 found"))
}
fn read_ints(filename: &str) -> anyhow::Result<Vec<i32>> {
let f = std::fs::File::open(filename)
.with_context(|| format!("couldn't find data file {}", filename))?;
let f = std::io::BufReader::new(f);
let ints: anyhow::Result<Vec<i32>> = f
.lines()
.map(|l| {
l.context("failed to read a line")?
.parse()
.context("failed to parse line into an integer")
})
.collect();
ints
}
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