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day18 part2

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This commit is contained in:
Glenn Griffin 2020-12-18 15:02:24 -08:00
parent f756bc105f
commit bd0fd7663f
1 changed files with 25 additions and 11 deletions
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36
src/day18.rs
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@ -20,20 +20,29 @@ fn num_or_paren_expr(i: &str) -> IResult<&str, usize> {
alt((num, paren_expr))(i)
}
fn expr(i: &str) -> IResult<&str, usize> {
fn add_or_sub(i: &str) -> IResult<&str, usize> {
let (i, lhs) = num_or_paren_expr(i)?;
fold_many0(
pair(
alt((char('+'), char('-'), char('*'), char('/'))),
num_or_paren_expr,
),
pair(alt((char('+'), char('-'))), num_or_paren_expr),
lhs,
|lhs, (op, rhs)| match op {
'+' => lhs + rhs,
'-' => lhs - rhs,
_ => unreachable!("invalid op"),
},
)(i)
}
fn expr(i: &str) -> IResult<&str, usize> {
let (i, lhs) = add_or_sub(i)?;
fold_many0(
pair(alt((char('*'), char('/'))), add_or_sub),
lhs,
|lhs, (op, rhs)| match op {
'*' => lhs * rhs,
'/' => lhs * rhs,
'/' => lhs / rhs,
_ => unreachable!("invalid op"),
},
)(i)
@ -44,6 +53,11 @@ fn solve_d18_p1(input: &str) -> usize {
input.split('\n').map(|line| expr(line).unwrap().1).sum()
}
#[aoc(day18, part2)]
fn solve_d18_p2(input: &str) -> usize {
input.split('\n').map(|line| expr(line).unwrap().1).sum()
}
#[cfg(test)]
mod tests {
use super::*;
@ -51,17 +65,17 @@ mod tests {
#[test]
fn test_expr() {
assert_eq!(expr("2+2"), Ok(("", 4)));
assert_eq!(expr("1 + 2 * 3 + 4 * 5 + 6"), Ok(("", 71)));
assert_eq!(expr("1 + 2 * 3 + 4 * 5 + 6"), Ok(("", 231)));
assert_eq!(expr("1 + (2 * 3) + (4 * (5 + 6))"), Ok(("", 51)));
assert_eq!(expr("2 * 3 + (4 * 5)"), Ok(("", 26)));
assert_eq!(expr("5 + (8 * 3 + 9 + 3 * 4 * 3)"), Ok(("", 437)));
assert_eq!(expr("2 * 3 + (4 * 5)"), Ok(("", 46)));
assert_eq!(expr("5 + (8 * 3 + 9 + 3 * 4 * 3)"), Ok(("", 1445)));
assert_eq!(
expr("5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4))"),
Ok(("", 12240))
Ok(("", 669060))
);
assert_eq!(
expr("((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2"),
Ok(("", 13632))
Ok(("", 23340))
);
}
}