2020: day18: part 2

This commit is contained in:
Antoine Martin 2020-12-18 15:50:04 +01:00
parent 426ea00636
commit e7dda32c74

View file

@ -18,6 +18,7 @@ pub fn run() -> Result<String> {
let mut res = String::with_capacity(128);
writeln!(res, "part 1: {}", part1(INPUT)?)?;
writeln!(res, "part 2: {}", part2(INPUT)?)?;
Ok(res)
}
@ -25,7 +26,22 @@ pub fn run() -> Result<String> {
fn part1(input: &str) -> Result<u64> {
input
.lines()
.map(|line| line.parse::<Expr>().map(|e| e.eval()))
.map(|line| {
terminated(expr, eof)(line)
.map_err(|_| anyhow!("couldn't parse expr"))
.map(|(_, e)| e.eval())
})
.sum()
}
fn part2(input: &str) -> Result<u64> {
input
.lines()
.map(|line| {
terminated(plus_priority, eof)(line)
.map_err(|_| anyhow!("couldn't parse expr"))
.map(|(_, e)| e.eval())
})
.sum()
}
@ -73,28 +89,57 @@ fn operator_expr(input: &str) -> IResult<&str, Expr> {
)(i)
}
fn plus(input: &str) -> IResult<&str, Expr> {
let (i, first_term) = term_plus_priority(input)?;
fold_many0(
pair(
delimited(char(' '), char('+'), char(' ')),
term_plus_priority,
),
first_term,
|acc, (_, val)| Expr::Op(Box::new(acc), Operator::Addition, Box::new(val)),
)(i)
}
fn mul(input: &str) -> IResult<&str, Expr> {
let (i, first_factor) = plus(input)?;
fold_many0(
pair(delimited(char(' '), char('*'), char(' ')), plus),
first_factor,
|acc, (_, val)| Expr::Op(Box::new(acc), Operator::Multiplication, Box::new(val)),
)(i)
}
fn num(input: &str) -> IResult<&str, Expr> {
map_res(take_while1(|c: char| c.is_digit(10)), |res: &str| {
res.parse().map(Expr::Num)
})(input)
}
fn paren(input: &str) -> IResult<&str, Expr> {
delimited(char('('), expr, char(')'))(input)
}
fn paren_plus_priority(input: &str) -> IResult<&str, Expr> {
delimited(char('('), plus_priority, char(')'))(input)
}
fn term(input: &str) -> IResult<&str, Expr> {
alt((delimited(char('('), expr, char(')')), num))(input)
alt((paren, num))(input)
}
fn term_plus_priority(input: &str) -> IResult<&str, Expr> {
alt((paren_plus_priority, num))(input)
}
fn expr(input: &str) -> IResult<&str, Expr> {
alt((operator_expr, term))(input)
}
impl std::str::FromStr for Expr {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self> {
let (_, res) = terminated(expr, eof)(s).map_err(|_| anyhow!("couldn't parse expr"))?;
Ok(res)
}
fn plus_priority(input: &str) -> IResult<&str, Expr> {
alt((mul, term_plus_priority))(input)
}
#[cfg(test)]
@ -112,9 +157,36 @@ mod tests {
("((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2", 13632),
];
for (expr, expected) in tests {
let expr: Expr = expr.parse().unwrap();
assert_eq!(expr.eval(), *expected);
for (exp, expected) in tests {
let (_, exp) = terminated(expr, eof)(exp).unwrap();
assert_eq!(exp.eval(), *expected);
}
}
#[test]
fn part1_real() {
assert_eq!(part1(INPUT).unwrap(), 800602729153);
}
#[test]
fn part2_provided() {
let tests = &[
("1 + 2 * 3 + 4 * 5 + 6", 231),
("1 + (2 * 3) + (4 * (5 + 6))", 51),
("2 * 3 + (4 * 5)", 46),
("5 + (8 * 3 + 9 + 3 * 4 * 3)", 1445),
("5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4))", 669060),
("((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2", 23340),
];
for (exp, expected) in tests {
let (_, exp) = terminated(plus_priority, eof)(exp).unwrap();
assert_eq!(exp.eval(), *expected);
}
}
#[test]
fn part2_real() {
assert_eq!(part2(INPUT).unwrap(), 92173009047076);
}
}