62 lines
1.6 KiB
Rust
62 lines
1.6 KiB
Rust
const TEST_INPUT: &'static str = "\
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7 6 4 2 1
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1 2 7 8 9
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9 7 6 2 1
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1 3 2 4 5
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8 6 4 4 1
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1 3 6 7 9\
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";
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const INPUT: &'static str = include_str!("../inputs/2024/day2.input");
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fn parse(i: &str) -> Vec<Vec<i32>> {
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i.lines().map(|l|
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l
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.split_whitespace()
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.map(|w| w.parse::<i32>().unwrap())
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.collect()
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).collect()
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}
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// Might make it not return a vector
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fn follows_rules(i: &Vec<i32>) -> Vec<bool> {
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let mut iter = i.iter();
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let first = iter.next().unwrap();
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let second = iter.next().unwrap();
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let initial_diff = second - first;
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let initial_holds = initial_diff.abs() <= 3 && initial_diff.abs() >= 1;
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let (acc, _, _) = iter.fold((vec![true, initial_holds], *second, initial_diff),
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|(mut acc, prev, prev_diff): (Vec<bool>, i32, i32), n: &i32| {
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let diff: i32 = n - prev;
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acc.push(
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diff.abs() <= 3 &&
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diff.abs() >= 1 &&
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((diff > 0 && prev_diff > 0) || (diff < 0 && prev_diff < 0))
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);
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(acc, *n, diff)
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});
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acc
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}
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fn try_without(mut l: Vec<i32>, index: usize) -> bool {
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l.remove(index);
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follows_rules(&l).iter().all(|x| *x)
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}
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pub fn part1() -> u32 {
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let input = parse(INPUT);
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input.iter().map(|l| if follows_rules(l).iter().all(|x| *x) { 1 } else { 0 }).sum()
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}
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pub fn part2() -> u32 {
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let mut input = parse(INPUT);
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input.iter_mut().map(|l| {
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let rules = follows_rules(l);
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if rules.iter().all(|x| *x) {
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1
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} else {
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l.iter().enumerate().any(|(i, _)| try_without(l.clone(), i)) as u32
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}
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}).sum()
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}
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