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type History = Vec<i64>;
#[derive(Debug)]
struct Report {
histories: Vec<History>,
}
impl From<&str> for Report {
fn from(report: &str) -> Self {
Self {
histories: report
.lines()
.map(|line| {
line.split_whitespace()
.map(|num| num.parse::<i64>().unwrap())
.collect::<History>()
})
.collect::<Vec<History>>(),
}
}
}
fn solve_part_one(data: &str) -> u64 {
let report = Report::from(data);
let mut ans = 0;
for history in report.histories.iter() {
let mut differences = vec![];
differences.push(history.clone());
while !differences.last().unwrap().iter().all(|&x| x == 0) {
differences.push(
differences
.last()
.unwrap()
.windows(2)
.map(|window| window[1] - window[0])
.collect::<Vec<_>>(),
)
}
for i in (0..differences.len() - 2).rev() {
let last_last = differences[i + 1].last().unwrap() + differences[i].last().unwrap();
differences[i].push(last_last);
}
ans += differences.first().unwrap().last().unwrap();
}
ans as u64
}
fn solve_part_two(data: &str) -> u64 {
let report = Report::from(data);
let mut ans = 0;
for history in report.histories.iter() {
let mut differences = vec![];
differences.push(history.clone());
while !differences.last().unwrap().iter().all(|&x| x == 0) {
differences.push(
differences
.last()
.unwrap()
.windows(2)
.map(|window| window[1] - window[0])
.collect::<Vec<_>>(),
)
}
for i in (0..differences.len() - 2).rev() {
let first_first = differences[i].first().unwrap() - differences[i + 1].first().unwrap();
differences[i].insert(0, first_first);
}
ans += differences.first().unwrap().first().unwrap();
}
ans as u64
}
fn main() {
let test_1 = include_str!("../input/day9_1.test");
let test_2 = include_str!("../input/day9_2.test");
let prod = include_str!("../input/day9.prod");
println!("part_1 test: {:?}", solve_part_one(test_1));
println!("part_1 prod {:?}", solve_part_one(prod));
println!("part_2 test: {:?}", solve_part_two(test_2));
println!("part_2 prod {:?}", solve_part_two(prod));
}
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