forked from ggriffiniii/aoc
82 lines
2.1 KiB
Rust
82 lines
2.1 KiB
Rust
use aoc_runner_derive::aoc;
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use nom::branch::alt;
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use nom::bytes::complete::tag;
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use nom::character::complete::{char, digit1, space0};
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use nom::combinator::map_res;
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use nom::multi::fold_many0;
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use nom::sequence::{delimited, pair};
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use nom::IResult;
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use std::str::FromStr;
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fn num(i: &str) -> IResult<&str, usize> {
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map_res(delimited(space0, digit1, space0), FromStr::from_str)(i)
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}
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fn paren_expr(i: &str) -> IResult<&str, usize> {
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delimited(space0, delimited(tag("("), expr, tag(")")), space0)(i)
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}
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fn num_or_paren_expr(i: &str) -> IResult<&str, usize> {
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alt((num, paren_expr))(i)
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}
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fn add_or_sub(i: &str) -> IResult<&str, usize> {
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let (i, lhs) = num_or_paren_expr(i)?;
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fold_many0(
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pair(alt((char('+'), char('-'))), num_or_paren_expr),
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lhs,
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|lhs, (op, rhs)| match op {
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'+' => lhs + rhs,
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'-' => lhs - rhs,
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_ => unreachable!("invalid op"),
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},
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)(i)
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}
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fn expr(i: &str) -> IResult<&str, usize> {
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let (i, lhs) = add_or_sub(i)?;
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fold_many0(
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pair(alt((char('*'), char('/'))), add_or_sub),
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lhs,
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|lhs, (op, rhs)| match op {
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'*' => lhs * rhs,
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'/' => lhs / rhs,
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_ => unreachable!("invalid op"),
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},
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)(i)
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}
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#[aoc(day18, part1)]
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fn solve_d18_p1(input: &str) -> usize {
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input.split('\n').map(|line| expr(line).unwrap().1).sum()
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}
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#[aoc(day18, part2)]
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fn solve_d18_p2(input: &str) -> usize {
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input.split('\n').map(|line| expr(line).unwrap().1).sum()
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_expr() {
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assert_eq!(expr("2+2"), Ok(("", 4)));
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assert_eq!(expr("1 + 2 * 3 + 4 * 5 + 6"), Ok(("", 231)));
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assert_eq!(expr("1 + (2 * 3) + (4 * (5 + 6))"), Ok(("", 51)));
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assert_eq!(expr("2 * 3 + (4 * 5)"), Ok(("", 46)));
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assert_eq!(expr("5 + (8 * 3 + 9 + 3 * 4 * 3)"), Ok(("", 1445)));
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assert_eq!(
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expr("5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4))"),
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Ok(("", 669060))
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);
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assert_eq!(
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expr("((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2"),
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Ok(("", 23340))
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);
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}
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}
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