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use std::collections::HashSet;
static DAY: u8 = 13;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", summarize_patterns(&input));
println!("{DAY}b: {}", summarize_patterns_with_smudge(&input));
}
#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
enum Reflection {
Vertical(usize),
Horizontal(usize),
}
impl Reflection {
fn summary(&self) -> usize {
match *self {
Reflection::Vertical(column) => column + 1,
Reflection::Horizontal(row) => (row + 1) * 100,
}
}
}
#[derive(Clone)]
struct Map {
pattern: Vec<Vec<bool>>,
}
impl Map {
fn new(input: &[String]) -> Map {
let mut pattern = Vec::new();
for line in input {
let row = line.chars()
.map(|c| c == '#')
.collect();
pattern.push(row);
}
Map { pattern }
}
fn _print_map(&self) {
for y in 0 .. self.pattern.len() {
for x in 0 .. self.pattern[0].len() {
if self.pattern[y][x] {
print!("#");
} else {
print!(".");
}
}
println!();
}
println!();
}
fn is_horizontal_reflection(&self, y: usize) -> bool {
for pair in (y+1 .. self.pattern.len()).zip((0 ..= y).rev()) {
if self.pattern[pair.0] != self.pattern[pair.1] {
return false;
}
}
true
}
fn is_vertical_reflection(&self, x: usize) -> bool {
for pair in (x+1 .. self.pattern[0].len()).zip((0 ..= x).rev()) {
for y in 0 .. self.pattern.len() {
if self.pattern[y][pair.0] != self.pattern[y][pair.1] {
return false;
}
}
}
true
}
fn find_reflections(&self) -> HashSet<Reflection> {
let mut reflections = HashSet::new();
for y in 0 .. self.pattern.len() - 1 {
if self.is_horizontal_reflection(y) {
reflections.insert(Reflection::Horizontal(y));
}
}
for x in 0 .. self.pattern[0].len() - 1 {
if self.is_vertical_reflection(x) {
reflections.insert(Reflection::Vertical(x));
}
}
reflections
}
fn find_reflection_with_smudge(&self) -> Reflection {
let orig_reflection = self.find_reflections();
for y in 0 .. self.pattern.len() {
for x in 0 .. self.pattern[0].len() {
let mut map = self.clone();
map.pattern[y][x] = !map.pattern[y][x];
let reflections = map.find_reflections();
let new_reflections = reflections.difference(&orig_reflection).collect::<Vec<_>>();
if !new_reflections.is_empty() {
return *new_reflections[0];
}
}
}
panic!("no reflection found");
}
}
fn summarize_patterns(input: &[String]) -> usize {
input.split(|line| line.is_empty())
.map(Map::new)
.map(|m| m.find_reflections().iter().next().unwrap().summary())
.sum()
}
fn summarize_patterns_with_smudge(input: &[String]) -> usize {
input.split(|line| line.is_empty())
.map(Map::new)
.map(|m| m.find_reflection_with_smudge().summary())
.sum()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"#.##..##.",
"..#.##.#.",
"##......#",
"##......#",
"..#.##.#.",
"..##..##.",
"#.#.##.#.",
"",
"#...##..#",
"#....#..#",
"..##..###",
"#####.##.",
"#####.##.",
"..##..###",
"#....#..#",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(summarize_patterns(&input), 405);
assert_eq!(summarize_patterns_with_smudge(&input), 400);
}
}
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