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use std::cmp::Ord;
use std::cmp::Ordering;
use std::collections::{BTreeMap, HashSet};
use std::io::{self, BufRead};
struct WireStep {
dir : char,
len : i32,
}
type WirePath = Vec<WireStep>;
#[derive(Clone, Debug)]
struct WirePoint {
wire: u8,
steps: usize,
}
#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd)]
// https://newspaint.wordpress.com/2016/07/05/implementing-custom-sort-for-btree-in-rust/
struct MapCoords {
x: i32,
y: i32,
}
type MapPoint = Vec<WirePoint>;
type WireMap = BTreeMap<MapCoords, MapPoint>;
impl Ord for MapCoords {
fn cmp(&self, other:&Self) -> Ordering {
let self_distance = i32::abs(self.x) + i32::abs(self.y);
let other_distance = i32::abs(other.x) + i32::abs(other.y);
if self_distance < other_distance {
Ordering::Less
} else if self_distance > other_distance {
Ordering::Greater
} else if self.y < other.y {
Ordering::Less
} else if self.y > other.y {
Ordering::Greater
} else if self.x < other.x {
Ordering::Less
} else if self.x > other.x {
Ordering::Greater
} else {
Ordering::Equal
}
}
}
fn read_input() -> Vec<WirePath> {
let stdin = io::stdin();
stdin.lock().lines()
.map(|line| {
line.unwrap().split(',').map(|s| WireStep {
dir: s.chars().next().unwrap(),
len: s.get(1..).unwrap().parse().unwrap(),
}).collect()
}).collect()
}
fn map_wire(wire: u8, path:&WirePath, map:&mut WireMap) {
let mut x = 0;
let mut y = 0;
let wp = WirePoint { wire, steps: 0 };
let mp = map.entry(MapCoords{x, y}).or_insert(vec![]);
mp.push(wp);
let mut steps = 0;
for trace in path.iter() {
for _ in 0..trace.len {
match trace.dir {
'U' => y -= 1,
'D' => y += 1,
'R' => x += 1,
'L' => x -= 1,
d => panic!("Invalid direction {}", d),
}
steps += 1;
let wp = WirePoint { wire, steps };
let mp = map.entry(MapCoords{x, y}).or_insert(vec![]);
mp.push(wp);
}
}
}
fn create_map(paths:&Vec<WirePath>, map:&mut WireMap) {
let mut wire_id = 1;
for path in paths.iter() {
map_wire(wire_id, path, map);
wire_id += 1;
}
}
fn find_intersections(wire_map:&WireMap) -> WireMap {
let mut ret = WireMap::new();
for (coords, wiring) in wire_map {
let wire_crossings = wiring.iter().map(|w| { w.wire }).collect::<HashSet<u8>>().len();
if wire_crossings > 1 && ! (coords.x == 0 && coords.y == 0) {
ret.insert(*coords, wiring.to_vec());
}
}
ret
}
fn first_puzzle(wire_paths:&Vec<WirePath>) -> Option<usize> {
let mut wire_map:WireMap = BTreeMap::new();
create_map(&wire_paths, &mut wire_map);
let intersections = find_intersections(&wire_map);
match intersections.iter().next() {
Some((c, _)) => Some((i32::abs(c.x) + i32::abs(c.y)) as usize),
_ => None,
}
}
fn second_puzzle(wire_paths:&Vec<WirePath>) -> Option<usize> {
let mut wire_map:WireMap = BTreeMap::new();
create_map(&wire_paths, &mut wire_map);
let intersections = find_intersections(&wire_map);
let lengths : Vec<usize> = intersections.iter().map(|(_, wiring)| {
wiring.iter().map(|w| { w.steps }).sum()
}).collect();
lengths.into_iter().min()
}
fn main() {
let wire_paths = read_input();
let first = first_puzzle(&wire_paths);
match first {
Some(s) => println!("Solution to first part: {}.", s),
_ => println!("No solution found for first part."),
}
let second = second_puzzle(&wire_paths);
match second {
Some(s) => println!("Solution to second part: {}.", s),
_ => println!("No solution found for second part."),
}
}
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