generated from fspoettel/advent-of-code-rust
/
21.rs
138 lines (122 loc) · 4 KB
/
21.rs
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advent_of_code::solution!(21);
use std::collections::VecDeque;
#[derive(Clone, Copy, Debug, Ord, PartialOrd, Eq, PartialEq, Hash)]
struct Position {
position: (usize, usize),
steps: usize,
}
pub struct Maze {
data: Vec<Vec<Spot>>,
xlen: usize,
ylen: usize,
first_position: (usize, usize),
position_list: Vec<Position>,
}
enum Spot {
Rock = 1,
Plot = 2,
}
impl Maze {
pub fn new(input: &str) -> Self {
let mut data = Vec::new();
let mut position = (0, 0);
let mut first_position: (usize, usize) = (0, 0);
for line in input.lines() {
let mut row = Vec::new();
for char in line.chars() {
match char {
'#' => {
row.push(Spot::Rock);
}
'.' => row.push(Spot::Plot),
'S' => {
row.push(Spot::Plot);
first_position = position;
}
_ => panic!("Invalid char"),
}
position.1 += 1;
}
data.push(row);
position.0 += 1;
position.1 = 0;
}
let xmax = data.len();
let ymax = data[0].len();
Self {
data,
xlen: xmax,
ylen: ymax,
first_position,
position_list: Vec::new(),
}
}
fn is_valid_plot(&self, x: i32, y: i32) -> bool {
if x < 0 || y < 0 {
return false;
}
if x >= self.xlen as i32 || y >= self.ylen as i32 {
return false;
}
let real_x = (x) as usize;
let real_y = (y) as usize;
match self.data[real_x][real_y] {
Spot::Plot => true,
_ => false,
}
}
fn get_four_directions(&self, position: &Position) -> Vec<Position> {
let mut four_elements : Vec<Position> = Vec::new();
let mut new_pos = position.clone();
new_pos.steps += 1;
new_pos.position.0 += 1;
four_elements.push(new_pos.clone());
new_pos.position.0 -= 2;
four_elements.push(new_pos.clone());
new_pos.position.0 += 1;
new_pos.position.1 += 1;
four_elements.push(new_pos.clone());
new_pos.position.1 -= 2;
four_elements.push(new_pos.clone());
four_elements
}
fn move_elf(&mut self) {
let mut pile: VecDeque<Position> = VecDeque::new();
pile.push_back(Position { position: self.first_position, steps: 0 });
while let Some(position) = pile.pop_front() {
for position in self.get_four_directions(&position) {
if self.is_valid_plot(position.position.0 as i32, position.position.1 as i32) {
if self.position_list.iter().filter(|&x| x.position == position.position).count() > 0 {
continue;
}
self.position_list.push(position);
pile.push_back(position);
}
}
}
}
fn part1(&mut self) -> usize {
self.position_list.iter().filter(|&x| x.steps < 65 && x.steps % 2 == 0).count()
}
fn part2(&mut self) -> usize{
let n = 202300;
let even_corners = self.position_list.iter().filter(|&x| x.steps % 2 == 0 && x.steps > 65).count();
let odd_corners = self.position_list.iter().filter(|&x| x.steps % 2 == 1 && x.steps > 65).count();
let even = self.position_list.iter().filter(|&k| k.steps % 2 == 1).count();
let odd = self.position_list.iter().filter(|&k| k.steps % 2 == 0).count();
(n + 1) * (n + 1) * even + n * n * odd - ((n + 1) * odd_corners) + (n * even_corners)
}
}
pub fn part_one(input: &str) -> Option<usize> {
let mut maze = Maze::new(input);
maze.move_elf();
Some(maze.part1())
}
pub fn part_two(input: &str) -> Option<usize> {
let mut maze = Maze::new(input);
maze.move_elf();
Some(maze.part2())
}
#[cfg(test)]
mod tests {
}