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use std::cmp::Ordering;
static DAY: u8 = 13;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", pair_indices(&input));
println!("{DAY}b: {}", decoder_key(&input));
}
#[derive(PartialEq,Eq,Debug)]
enum PacketData {
Int { value: u32 },
List { value: Vec<PacketData> },
}
#[derive(PartialEq,Eq,Debug,PartialOrd,Ord)]
enum ComparisonResult {
True,
False,
Next,
}
impl PacketData {
fn new(input: &str) -> PacketData {
let mut datalist = Vec::new();
let mut head = PacketData::List { value: Vec::new() };
let mut number = None;
assert_eq!(input.chars().next().unwrap(), '[');
for c in input.chars() {
match c {
'[' => {
datalist.push(head);
head = PacketData::List { value: Vec::new() };
},
']' => {
let mut parent = datalist.pop().expect("list should not be empty");
match parent {
PacketData::Int { value: _ } => panic!("parent should be a list"),
PacketData::List { ref mut value } => {
if let Some(n) = number {
match head {
PacketData::List { ref mut value } => value.push(PacketData::Int { value: n }),
PacketData::Int { value: _ } => panic!("head should be a list"),
}
number = None;
}
value.push(head);
head = parent;
}
}
},
digit if c.is_ascii_digit() => {
let digit = digit.to_digit(10).unwrap();
match number {
None => number = Some(digit),
Some(n) => {
number = Some(n * 10 + digit);
}
}
},
',' => {
if let Some(n) = number {
match head {
PacketData::List { ref mut value } => value.push(PacketData::Int { value: n }),
PacketData::Int { value: _ } => panic!("head should be a list"),
}
number = None;
}
/* if previous char waas ], it has already been handled */
}
_ => unimplemented!(),
}
}
match head {
PacketData::List { mut value } => value.pop().unwrap(),
PacketData::Int { value: _ } => panic!("head should have a list"),
}
}
fn right_order(left: &PacketData, right: &PacketData) -> ComparisonResult {
match left {
PacketData::Int { value: val_left } => {
match right {
PacketData::Int { value: val_right } => match val_left.cmp(val_right) {
Ordering::Less => ComparisonResult::True,
Ordering::Greater => ComparisonResult::False,
Ordering::Equal => ComparisonResult::Next,
}
PacketData::List { value: _val_right } => {
let new_left = PacketData::new(&format!("[{}]", val_left));
PacketData::right_order(&new_left, right)
}
}
},
PacketData::List { value: val_left } => {
match right {
PacketData::Int { value: val_right } => {
let new_right = PacketData::new(&format!("[{}]", val_right));
PacketData::right_order(left, &new_right)
},
PacketData::List { value: val_right } => {
for (item_left, item_right) in val_left.iter().zip(val_right.iter()) {
let result = PacketData::right_order(item_left, item_right);
match result {
ComparisonResult::Next => continue,
res => return res,
}
}
match val_left.len().cmp(&val_right.len()) {
Ordering::Less => ComparisonResult::True,
Ordering::Greater => ComparisonResult::False,
Ordering::Equal => ComparisonResult::Next,
}
}
}
}
}
}
}
impl PartialOrd for PacketData {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for PacketData {
fn cmp(&self, other: &Self) -> Ordering {
match PacketData::right_order(self, other) {
ComparisonResult::True => Ordering::Less,
_ => Ordering::Greater,
}
}
}
fn pair_indices(input: &[String]) -> usize {
input.chunks(3)
.map(|c| (PacketData::new(&c[0]), PacketData::new(&c[1])))
.enumerate()
.filter(|(_,pair)| PacketData::right_order(&pair.0, &pair.1) == ComparisonResult::True)
.map(|(idx,_)| idx + 1)
.sum()
}
fn decoder_key(input: &[String]) -> usize {
let mut input = Vec::from(input);
input.push("[[2]]".to_string());
input.push("[[6]]".to_string());
let mut input = input.iter()
.filter(|line| !line.is_empty())
.map(|line| PacketData::new(line))
.collect::<Vec<_>>();
input.sort();
let packet2 = PacketData::new("[[2]]");
let packet6 = PacketData::new("[[6]]");
input.iter()
.enumerate()
.filter(|&(_,packet)| [&packet2, &packet6].contains(&packet))
.map(|(pos,_)| pos + 1)
.product()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
"[1,1,3,1,1]",
"[1,1,5,1,1]",
"",
"[[1],[2,3,4]]",
"[[1],4]",
"",
"[9]",
"[[8,7,6]]",
"",
"[[4,4],4,4]",
"[[4,4],4,4,4]",
"",
"[7,7,7,7]",
"[7,7,7]",
"",
"[]",
"[3]",
"",
"[[[]]]",
"[[]]",
"",
"[1,[2,[3,[4,[5,6,7]]]],8,9]",
"[1,[2,[3,[4,[5,6,0]]]],8,9]",
].iter().map(|&x| String::from(x)).collect::<Vec<_>>();
assert_eq!(pair_indices(&input), 13);
assert_eq!(decoder_key(&input), 140);
}
}
|
