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main.rs
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main.rs
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use std::io::{self, BufRead};
#[derive(PartialEq, Eq, Clone, Debug)]
enum Elem {
Open,
Close,
Num(i32),
}
type Expr = Vec<Elem>;
fn main() {
let stdin = io::stdin();
let mut lines = stdin.lock().lines();
let mut expr = parse_expr(lines.next().unwrap().unwrap());
for _line in lines {
let line = _line.unwrap();
let mut new_expr = parse_expr(line);
expr = add(&expr, &mut new_expr);
}
println!("{:?}", eval(&expr).unwrap());
}
fn parse_expr(str: String) -> Expr {
let mut expr = Expr::new();
for c in str.replace(",", "").chars() {
expr.push(match c {
'[' => Elem::Open,
']' => Elem::Close,
_ => Elem::Num(c.to_string().parse::<i32>().unwrap()),
});
}
expr
}
fn add(e1: &Expr, e2: &Expr) -> Expr {
let mut expr = e1.clone();
expr.extend(e2.clone());
expr.insert(0, Elem::Open);
expr.push(Elem::Close);
loop {
let (e, changed) = explode(&expr);
expr = e;
if changed {
continue;
}
let (e, changed) = split(&expr);
expr = e;
if changed {
continue;
}
break;
}
expr
}
fn explode(expr: &Expr) -> (Expr, bool) {
let mut new_expr = expr.clone();
let mut explode_index: usize = 0;
let mut is_explode = false;
let mut depth = 0;
for i in 0..expr.len() - 1 {
match expr[i] {
Elem::Open => {
depth += 1;
}
Elem::Close => {
depth -= 1;
}
Elem::Num(_) => {
if matches!(expr[i + 1], Elem::Num(_)) && depth > 4 {
is_explode = true;
explode_index = i;
break;
}
}
};
}
if is_explode {
for i in (0..explode_index).rev() {
if let Elem::Num(n) = expr[i] {
if let Elem::Num(left_n) = expr[explode_index] {
new_expr[i] = Elem::Num(n + left_n);
break;
}
}
}
for i in explode_index + 2..expr.len() {
if let Elem::Num(n) = expr[i] {
if let Elem::Num(right_n) = expr[explode_index + 1] {
new_expr[i] = Elem::Num(n + right_n);
break;
}
}
}
new_expr.remove(explode_index);
new_expr.remove(explode_index);
new_expr.remove(explode_index);
new_expr[explode_index - 1] = Elem::Num(0);
}
(new_expr, is_explode)
}
fn split(expr: &Expr) -> (Expr, bool) {
let mut new_expr = expr.clone();
for i in 0..expr.len() - 1 {
match expr[i] {
Elem::Num(n) => {
if n > 9 {
new_expr.remove(i);
new_expr.insert(i, Elem::Close);
new_expr.insert(i, Elem::Num((n as f64 / 2.0).ceil() as i32));
new_expr.insert(i, Elem::Num((n as f64 / 2.0).floor() as i32));
new_expr.insert(i, Elem::Open);
return (new_expr, true);
}
}
_ => (),
};
}
return (new_expr, false);
}
fn eval(expr: &Expr) -> Result<i32, ()> {
let mut new_expr = expr.clone();
while new_expr.len() != 1 {
for i in 0..new_expr.len() - 1 {
if let Elem::Num(n1) = new_expr[i] {
if let Elem::Num(n2) = new_expr[i + 1] {
new_expr.remove(i);
new_expr.remove(i);
new_expr.remove(i);
new_expr[i - 1] = Elem::Num(n1 * 3 + n2 * 2);
break;
}
}
}
}
if let Elem::Num(n) = new_expr[0] {
Ok(n)
} else {
Err(())
}
}