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use std::collections::VecDeque;
use regex::Regex;
static DAY: u8 = 5;
fn main() {
let input = advent::read_lines(DAY);
println!("{DAY}a: {}", find_top_crates(&input));
println!("{DAY}b: {}", find_top_crates_9001(&input));
}
struct CrateMover {
instructions: Vec<Instruction>,
stacks: Vec<VecDeque<char>>,
}
struct Instruction {
amount: usize,
from: usize,
to: usize,
}
impl CrateMover {
fn new(input: &[String]) -> CrateMover {
let re_instruction = Regex::new("move ([0-9]+) from ([0-9]+) to ([0-9]+)").unwrap();
let mut instructions = Vec::new();
let mut stacks = Vec::new();
for line in input {
if let Some(cap) = re_instruction.captures(line) {
instructions.push(Instruction {
amount: cap[1].parse::<usize>().unwrap(),
from: cap[2].parse::<usize>().unwrap() - 1,
to: cap[3].parse::<usize>().unwrap() - 1,
});
}
if line.find('[').is_some() {
let chars = line.chars().collect::<Vec<_>>();
for (index, chunk) in chars.chunks(4).enumerate() {
// chunk: "[x] "
let name = chunk[1];
if name == ' ' {
// empty position
continue;
}
if index >= stacks.len() {
stacks.resize(index + 1, VecDeque::new());
}
stacks[index].push_front(name);
}
}
}
CrateMover { stacks, instructions }
}
fn move_crates(&mut self) {
for instruction in &self.instructions {
for _ in 0 .. instruction.amount {
let name = self.stacks[instruction.from].pop_back().expect("Stack has no crate");
self.stacks[instruction.to].push_back(name);
}
}
}
fn move_crates_9001(&mut self) {
for instruction in &self.instructions {
let drain_from = self.stacks[instruction.from].len() - instruction.amount;
let moved_stack = self.stacks[instruction.from].drain(drain_from ..).collect::<Vec<_>>();
self.stacks[instruction.to].extend(moved_stack);
}
}
}
fn find_top_crates(input: &[String]) -> String {
let mut cratemover = CrateMover::new(input);
cratemover.move_crates();
cratemover.stacks.iter()
.map(|stack| stack.back().unwrap())
.collect()
}
fn find_top_crates_9001(input: &[String]) -> String {
let mut cratemover = CrateMover::new(input);
cratemover.move_crates_9001();
cratemover.stacks.iter()
.map(|stack| stack.back().unwrap())
.collect()
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn test() {
let input = [
" [D] ".to_string(),
"[N] [C] ".to_string(),
"[Z] [M] [P]".to_string(),
" 1 2 3 ".to_string(),
"".to_string(),
"move 1 from 2 to 1".to_string(),
"move 3 from 1 to 3".to_string(),
"move 2 from 2 to 1".to_string(),
"move 1 from 1 to 2".to_string(),
];
assert_eq!(find_top_crates(&input), "CMZ");
assert_eq!(find_top_crates_9001(&input), "MCD");
}
}
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