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#[derive(PartialEq, Clone, Copy)]
enum Direction {
Up,
Down,
Unknown,
}
use Direction::*;
fn is_safe(levels: &[u32]) -> bool {
let mut direction = Unknown;
for i in 0..levels.len() - 1 {
let [x, y] = levels[i..=i + 1] else {
unreachable!()
};
let (diff, d) = if x > y { (x - y, Down) } else { (y - x, Up) };
if direction == Unknown {
direction = d;
}
if diff == 0 || diff > 3 || direction != d {
return false;
}
}
true
}
fn p1(input: &str) -> String {
let mut total = 0;
for report in input.lines() {
let levels: Vec<u32> = report
.split_whitespace()
.map(|l| l.parse().unwrap())
.collect();
if is_safe(&levels) {
total += 1;
}
}
total.to_string()
}
fn is_safe_with_dampener(levels: &[u32]) -> bool {
for i in 0..levels.len() {
let mut levels_without_i: Vec<u32> = levels.to_vec();
levels_without_i.remove(i);
if is_safe(&levels_without_i) {
return true;
}
}
false
}
fn p2(input: &str) -> String {
let mut total = 0;
for report in input.lines() {
let levels: Vec<u32> = report
.split_whitespace()
.map(|l| l.parse().unwrap())
.collect();
if is_safe(&levels) || is_safe_with_dampener(&levels) {
total += 1;
}
}
total.to_string()
}
fn main() {
aoc2024::run_day("2", p1, p2);
}
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