55 lines
1.4 KiB
Rust
55 lines
1.4 KiB
Rust
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use aoc_runner_derive::{aoc, aoc_generator};
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use nom::character::complete::multispace0;
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use nom::multi::many1;
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use nom::{character::complete::u64 as parse_u64, IResult};
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#[aoc_generator(day1)]
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pub fn generator(input: &str) -> Vec<(u64, u64)> {
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many1(parse_line)(input).unwrap().1
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}
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fn parse_line(input: &str) -> IResult<&str, (u64, u64)> {
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let (input, left) = parse_u64(input)?;
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let (input, _) = multispace0(input)?;
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let (input, right) = parse_u64(input)?;
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let (input, _) = multispace0(input)?;
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Ok((input, (left, right)))
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}
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#[aoc(day1, part1)]
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pub fn part1(input: &[(u64, u64)]) -> u64 {
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let (mut left, mut right): (Vec<u64>, Vec<u64>) = input.iter().copied().unzip();
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left.sort();
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right.sort();
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left.iter()
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.zip(right.iter())
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.map(|(l, r)| (*l).abs_diff(*r))
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.sum()
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}
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#[aoc(day1, part2)]
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pub fn part2(input: &[(u64, u64)]) -> usize {
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let (mut left, mut right): (Vec<u64>, Vec<u64>) = input.iter().copied().unzip();
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left.sort();
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right.sort();
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let mut l;
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let mut r = 0;
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let mut score = 0usize;
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for value in left {
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l = r;
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while l < right.len() && right[l] < value {
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l += 1
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}
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r = l;
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while r < right.len() && right[r] <= value {
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r += 1
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}
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score += (value as usize) * (r - l);
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if r == right.len() - 1 {
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break;
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};
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}
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score
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}
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