done with day9 part1
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64
2022-aoc/src/d9.rs
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64
2022-aoc/src/d9.rs
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@ -0,0 +1,64 @@
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use std::collections::HashSet;
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use aoc_runner_derive::{aoc as aoc_run, aoc_generator};
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type Position = (i32, i32);
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#[aoc_generator(day9)]
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fn parse_input(input: &str) -> Vec<Position> {
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let mut out = Vec::new();
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let (mut x, mut y) = (0, 0);
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out.push((x, y));
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for line in input.lines() {
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let mut split = line.split_ascii_whitespace();
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let dir = split.next().unwrap();
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let num: i32 = split.next().unwrap().parse().unwrap();
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for _ in 0..num {
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match dir {
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"U" => y += 1,
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"D" => y -= 1,
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"L" => x -= 1,
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"R" => x += 1,
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_ => unreachable!(),
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}
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out.push((x, y));
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}
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}
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out
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}
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#[aoc_run(day9, part1)]
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fn part1(input: &[Position]) -> usize {
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let mut tail = (0, 0);
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let mut set = HashSet::new();
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set.insert(tail);
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for mv in input {
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tail = new_tail(mv, &tail);
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set.insert(tail);
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}
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set.len()
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}
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#[aoc_run(day9, part2)]
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fn part2(input: &[Position]) -> u32 {
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0
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}
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fn new_tail(head: &Position, tail: &Position) -> Position {
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let dy = head.1 - tail.1;
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let dx = head.0 - tail.0;
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match (dx, dy) {
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(0, 0) => *tail,
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(n, m) if (n.abs() == 1) && (m.abs() == 1) => *tail,
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(n, 0) | (0, n) if n.abs() == 1 => *tail,
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(_, 2) | (_, -2) if dx.abs() == 1 => (tail.0 + dx, tail.1 + (dy / 2)),
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(2, y) | (-2, y) if y.abs() == 1 => {
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let sign = dx / dx.abs();
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(tail.0 + sign * (dx.abs() - 1), tail.1 + dy)
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}
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(n, _) if n.abs() == 2 => (tail.0 + n / 2, tail.1),
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(_, n) if n.abs() == 2 => (tail.0, tail.1 + n / 2),
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_ => unreachable!("got {:?}", (dx, dy)),
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}
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}
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@ -8,5 +8,6 @@ mod d5;
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mod d6;
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mod d7;
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mod d8;
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mod d9;
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aoc_lib! { year = 2022 }
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