From efe7c0f1e1c20cb69e52eb501b392ebf4526ec1e Mon Sep 17 00:00:00 2001 From: Sam Willcocks Date: Thu, 15 Dec 2022 13:20:33 +0000 Subject: [PATCH] Add day3 part1 --- src/bin/day3.rs | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) create mode 100644 src/bin/day3.rs diff --git a/src/bin/day3.rs b/src/bin/day3.rs new file mode 100644 index 0000000..810c108 --- /dev/null +++ b/src/bin/day3.rs @@ -0,0 +1,38 @@ +/** 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::>()?; // "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::::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::() // Sum the priorities of items in common in each "rucksack" + }) + .sum(); // Sum all the rucksacks' priorities + println!("Part 1: {}", sum); + Ok(()) +}