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day9 solution

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Andrew Coleman 2023-12-10 14:57:00 -05:00
parent c43f19f2e3
commit 5b2760e9f7
2 changed files with 76 additions and 0 deletions

75
2023/src/day09.rs Normal file
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@ -0,0 +1,75 @@
use aoc_runner_derive::{aoc, aoc_generator};
type Seq = Vec<i64>;
fn all_zero(s: &Seq) -> bool {
s.iter().find(|t| **t != 0).is_none()
}
#[aoc_generator(day9)]
fn parse(input: &str) -> Vec<Seq> {
input
.lines()
.filter_map(|line| {
if !line.is_empty() {
let nums = line.split(" ").map(|n| n.parse::<i64>().unwrap()).collect();
Some(nums)
} else {
None
}
})
.collect()
}
fn get_diffs(s: &Seq) -> Seq {
let mut result: Seq = vec![];
for index in 0..(s.len() - 1) {
result.push(s[index + 1] - s[index]);
}
result
}
fn next_number(s: &Seq) -> i64 {
if all_zero(s) {
0
} else {
let d = get_diffs(s);
s.last().unwrap() + next_number(&d)
}
}
#[aoc(day9, part1)]
fn part1(input: &[Seq]) -> i64 {
input.iter().map(|s| next_number(&s)).sum()
}
fn previous_number(s: &Seq) -> i64 {
if all_zero(s) {
0
} else {
let d = get_diffs(s);
s[0] - previous_number(&d)
}
}
#[aoc(day9, part2)]
fn part2(input: &[Seq]) -> i64 {
input.iter().map(|s| previous_number(&s)).sum()
}
#[cfg(test)]
mod tests {
use super::*;
const SAMPLE_DATA: &'static str = r#"0 3 6 9 12 15
1 3 6 10 15 21
10 13 16 21 30 45
"#;
#[test]
fn sample_data() {
let input = parse(&SAMPLE_DATA);
assert_eq!(part1(&input), 114);
assert_eq!(part2(&input), 2);
}
}

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@ -8,5 +8,6 @@ mod day05;
mod day06;
mod day07;
mod day08;
mod day09;
aoc_lib! { year = 2023 }