86 lines
2.4 KiB
Rust
86 lines
2.4 KiB
Rust
// ==== day 12
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use crate::utils;
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use anyhow::Result;
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use std::mem;
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fn navigate(data: &str) -> usize {
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let mut heading = 90;
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let (mut pos_n, mut pos_e) = (0, 0);
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data.lines().for_each(|l| {
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let dir = &l[0..1];
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let dist = &l[1..].parse::<i64>().expect("int parse error");
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match dir {
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"N" => pos_n += dist,
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"S" => pos_n -= dist,
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"E" => pos_e += dist,
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"W" => pos_e -= dist,
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"L" => heading = (heading + 360 - dist) % 360,
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"R" => heading = (heading + dist) % 360,
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"F" => match heading {
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0 => pos_n += dist,
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90 => pos_e += dist,
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180 => pos_n -= dist,
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270 => pos_e -= dist,
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360 => pos_n += dist,
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_ => panic!("non cardinal heading!"),
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},
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_ => panic!("bad direction!"),
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}
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});
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(pos_n.abs() + pos_e.abs()) as usize
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}
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fn navigate2(data: &str) -> usize {
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let (mut wpt_n, mut wpt_e) = (1, 10);
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let (mut ship_n, mut ship_e) = (0, 0);
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data.lines().for_each(|l| {
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let dir = &l[0..1];
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let dist = &l[1..].parse::<i64>().expect("int parse error");
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match dir {
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"N" => wpt_n += dist,
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"S" => wpt_n -= dist,
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"E" => wpt_e += dist,
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"W" => wpt_e -= dist,
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"L" | "R" => match (dir, dist) {
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("L", 90) | ("R", 270) => {
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wpt_n = -wpt_n;
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mem::swap(&mut wpt_n, &mut wpt_e);
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}
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("L", 270) | ("R", 90) => {
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wpt_e = -wpt_e;
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mem::swap(&mut wpt_n, &mut wpt_e);
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}
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(_, 180) => {
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wpt_n = -wpt_n;
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wpt_e = -wpt_e;
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}
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_ => panic!("bad direction!"),
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},
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"F" => {
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ship_n += dist * wpt_n;
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ship_e += dist * wpt_e;
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}
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_ => panic!("bad direction!"),
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}
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});
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(ship_n.abs() + ship_e.abs()) as usize
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}
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// main
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pub fn run() -> Result<(usize, usize)> {
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let data = utils::read_file("data/input-12.txt")?;
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let answers = utils::read_i64s("data/output-12.txt")?;
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let p1 = navigate(&data);
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let p2 = navigate2(&data);
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assert_eq!(p1, answers[0] as usize);
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assert_eq!(p2, answers[1] as usize);
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Ok((p1, p2))
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}
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