39 lines
1.6 KiB
Rust
39 lines
1.6 KiB
Rust
|
/** Solution for Advent of Code 2022 day 3.
|
||
|
|
* https://adventofcode.com/2022/day/3
|
||
|
|
*/
|
||
|
|
use aoc2022::StdError;
|
||
|
|
use std::collections::HashSet;
|
||
|
|
use std::fs::File;
|
||
|
|
use std::io::{BufRead, BufReader};
|
||
|
|
|
||
|
|
fn main() -> StdError<()> {
|
||
|
|
// Open the input file and split all the lines.
|
||
|
|
let lines: Vec<_> = BufReader::new(File::open("input/day3.txt")?)
|
||
|
|
.lines()
|
||
|
|
.collect::<Result<_, _>>()?; // "Short circuit" any Errors in the iterator
|
||
|
|
|
||
|
|
let sum: u32 = lines
|
||
|
|
.iter()
|
||
|
|
.map(|l| {
|
||
|
|
assert!(l.len() % 2 == 0); // We won't be able to evenly split a odd-length line!
|
||
|
|
let (one, two) = (&l[0..l.len() / 2], &l[l.len() / 2..]);
|
||
|
|
|
||
|
|
// Make sets out of the characters in each compartment...
|
||
|
|
HashSet::<char>::from_iter(one.chars())
|
||
|
|
// ... then calculate the intersection, giving us the "items" (chars) in common
|
||
|
|
.intersection(&HashSet::from_iter(two.chars()))
|
||
|
|
.map(|c| match c {
|
||
|
|
// Now, we map our "items" to their "priorities".
|
||
|
|
// Fortunately we can cast all chars to u32, which makes this a matter of some
|
||
|
|
// simple arithmetic.
|
||
|
|
'a'..='z' => (*c as u32) - 'a' as u32 + 1,
|
||
|
|
'A'..='Z' => (*c as u32) - 'A' as u32 + 27,
|
||
|
|
_ => panic!("Got non-ascii alphabetic char!"),
|
||
|
|
})
|
||
|
|
.sum::<u32>() // Sum the priorities of items in common in each "rucksack"
|
||
|
|
})
|
||
|
|
.sum(); // Sum all the rucksacks' priorities
|
||
|
|
println!("Part 1: {}", sum);
|
||
|
|
Ok(())
|
||
|
|
}
|