A fun one! Day 18 done.

Cargo.toml

@@ -3,11 +3,16 @@ name = "advent2020"
 version = "0.1.0"
 authors = ["Adam Wick <awick@uhsure.com>"]
 edition = "2018"
+build = "build.rs"
 
 [dependencies]
+lalrpop-util = "0.19.1"
 nom = "6.0.1"
 petgraph = "0.5.1"
 thiserror = "1.0.22"
 
+[build-dependencies]
+lalrpop = { version = "0.19.1", features = ["lexer"] }
+
 [profile.release]
 debug = 1

build.rs

@@ -0,0 +1,3 @@
+fn main() {
+    lalrpop::process_root().unwrap();
+}

inputs/day18.txt

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+5 + (2 * 4 * 4 + 4 + (4 * 8 + 9 + 3 + 4) * 9)
+(8 * 5 + 8 * 7 + (5 + 5) + 5) * (7 + 4 + 5) * (4 + 8 + 2 * 6)
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+(7 * 2 * 5 * (9 + 7 + 4) * 5) * 2
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+(7 * 7 + 8 * 2 * (6 + 8 + 7 * 2 + 8 + 5) * 4) + 2 * ((9 + 6) + 6 + 4 + 8 + 6 + 8) * 4 + 7
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+9 + (8 + 4 + 6 * 6 + 7) + (4 + 2 + 2 + (7 + 5 * 7 * 7 + 9 * 6)) + (2 * 9 * 5 * 6) * 8
+(8 + 4) + 5 * 9 + (6 + 6 * 2 * 4) + ((7 + 7 * 8) * 7 + (7 * 5 * 9) + 2) * 7
+5 * 6
+9 + (9 + 7 + 6 + 5 * 5 + 8) + 3 + 9 * (9 + 9) + 7
+(7 * 4 * 5 * 8 + 4 + 5) + 3 * (9 + 3 * 3 + 4 * 2) + 4 * 3
+3 + 3 * 2 * 6 + 2
+7 + 6 * 6 * 9 + (7 + 7 + 4 + 8 * (3 + 9))
+4 * ((2 + 7 * 5 + 6) + 8 + 5 + 7 * 7) * 8
+(6 * 9 * (7 * 3 + 8 + 3 * 3) + 4 * 6 * 4) * 3 * 6 + 9 + 3 + 6
+5 * 4 + 7 * (2 * 3) + (8 * 2 + 5) * 7
+2 * 7 * 8 * (4 + 3 + 4 + 6)
+7 + 7 + (4 + (2 * 8 + 9) + 2 + 5) * 8 + 2
+(6 + (2 + 9 * 4 * 8) * 5 * (4 * 5 + 6 + 2) * 6) + (6 * 6 + 7 * 9) + 4 * 3
+7 + 5
+3 * 2 + 2 * 8 * (2 * 2 * 4 + 5 * 2 * 5) + ((8 * 8 + 6 + 4 * 4 * 5) * 3 + 6 + 8)
+8 + ((8 * 5) + (6 + 7) + 8 + 7 * (5 + 8)) + 5
+5 + (4 * 6)
+5 * 2 + 3 + ((7 + 5 + 5 * 5 * 7) * (2 * 8 + 9)) + 6
+(3 * 8 * 5 + (6 * 4 + 4 * 8) + 8) * 6 + (3 * 7 * 6 + 4 * 8) * 3 * (8 + 8 + 5)
+7 + 8 + 2 * (8 * 6) * 6
+3 * (9 * (3 + 7)) * (7 + (4 * 6) + 8 + 8 + 4 * 9) + (3 * 4 + (6 + 8 + 2 + 7 + 7) * 3 * 7)
+(6 * (9 + 4 + 9) + (8 + 9 + 9)) + 7 * 8 * 8 + ((9 + 5 + 7 * 2) + 8 + 6 * 4) * 9
+7 + (9 + (5 * 6 + 2 * 9) * 2) + 2
+(9 + 3 * 2 * 8 + 7 + 8) * 2 * (2 + 2)
+7 + 4 + (7 * 7 * 6 + 3 + (4 + 5)) * 9
+9 * 5 + (3 * 7 * 4 + 6 * (2 + 2 * 4 + 3 + 3) + (7 * 4 * 5)) + (8 + (9 + 5) * 6) + 3
+8 * 8 + 6 + 2 + (8 + 7 + 2 + 3 * 5) * 8
+9 + 8 + 8 + (9 * 2 * 9 * 9 * (7 + 6 * 7))
+7 * (8 + (5 + 5 * 8 * 3 + 4) + 2 + 4 * 6 + 4) + 8 * 9
+9 + 3 * ((8 + 9) * 4 + 8 + 3) * (8 + 7) * (9 + 2 * 5 + (5 + 4 * 2 * 7 + 9 + 8))
+8 * 7
+(5 + (9 * 5 * 9) * 6 * 4 * (4 * 6) * (6 + 8 + 7 * 5)) * 4 + 6 * 9
+7 + 5 * 2 + (4 + 5) + 6 + (9 * 4)
+3 * 5 + (5 + 9 + 8)
+((2 * 6) + 2) + 4 * 9
+3 + 8 * ((2 * 6 + 6) * (9 * 8 + 8) + (6 + 6 * 6 * 5)) + 5 + 4
+(4 + (2 + 4) + 6 + 9) * (5 * 2 * 2) * 9 + 6 * (5 * (7 * 4 * 8 + 3 + 9) * 2 + 3 * (2 + 4 + 8 * 9))
+6 * (6 + 5 * 4 * 9 + 9 + (3 * 2 + 3)) + 6 + 7
+3 * (4 + 4) + 4 * 5 + 6
+(8 * 6 * 3 + 7 * 7) + 3
+(4 * 6 * 7 * 8 + (8 * 7 + 9 * 5 * 7) + (8 + 7)) * 7 * 7
+5 + 8 + 5 * 4 + 3 * ((5 * 9 + 9) * 2 + 3 + 2 + 2 * (2 * 3 + 8 + 5 * 6 + 6))
+(8 * 5 + 3 * (8 + 9 * 4 * 5 + 9) * 4 + 9) * 2 + 7 + 3 + 7 + 9
+4 + ((8 * 4 + 5 + 7 + 2 * 6) * (7 + 2) + (6 + 2 + 2 * 4 * 7 + 4) + 5) * 9 + 7 * (8 * 4 + (3 + 5) + 7 * 2)
+8 * (8 * (5 * 6 * 8) + 9 * 9 * 4) * 3
+7 * (9 + 5 * (5 + 5 + 7 * 7) + 4)
+8 + 4 + 9 + 5 * (9 + (7 + 2 + 9) * 3 + 3 * 7) + (7 * 7)
+4 * 2 + 7 * (7 * 7 * 9 + (6 + 2 + 8 + 7) + 4 * 2) + (5 * 7)
+4 * ((5 + 9 * 5 * 6 * 9) * 3) * 8 * (4 + (7 * 7 * 9 * 6))
+9 + 9 * 9 * (4 * 6 * 4 * 7 + 7) + ((5 * 9 + 4 * 4 + 2 + 4) * 7 * 6 * 5) + 8
+4 + 4 * (4 * 5 * (6 + 9) * 5 * 5 + 2) + (4 * (8 * 2 * 9 + 8) + 2 * 9) * 3 + 2
+3 * 7 + 3 * ((3 + 2 * 9 * 5 + 5) + (3 + 5 * 7 + 2 + 6) * (5 * 8 * 8 + 7 + 8 + 4)) * 4 + 3
+(2 * 5 * 4 + 3) * 5 + 8 * 4 + 7 * 4
+5 * 3 + 3 * 4 * 7 + (6 + 4 + 8 * 7 + 4)
+2 + 2 + (7 + 2 + (9 * 7 + 6 + 4 * 2)) + 9 * ((9 * 4 + 4) * 6 * 8 * 5 * 6)
+8 + 2
+8 + 3 + 4 + ((5 + 3 + 7) * 3 + 4 + 4) + 8
+9 + 9 + 2 + (2 * (5 + 4 * 2 + 4)) + (2 + 6 * 2)
+2 + (5 + 5 * 6)
+2 * 9 + 4 * ((9 * 3 * 2 * 7 * 7) * 8 * 6 + 4)
+4 + 5 + 9 + (8 + 6 + 3) + (6 + 9 + 4 + 5) * 2
+4 + 3 * 7 + ((3 + 3) * 6 + (4 * 6 * 3 + 9 * 6)) + 8 * 2
+7 + 7 + ((4 * 8 + 8) * 7 * 3 * 5 + 3 * 2) + 2 + 8
+(7 + 5 * 2 + 8 * (5 * 3 * 4 * 4 + 7 * 5)) * ((3 * 3 + 8) * (4 + 9)) * 7
+6 * 9 + 5 * 7 * 7
+4 * 2 + (4 + 6 + 3 * 3) * 2 + (9 * 6) + 9
+3 + 6 + (3 * 8 * (6 + 3 + 4 * 7) + 4 + (7 * 8))
+7 * 4 + 5 + 6 * 7 * (8 * 4 + (4 * 6 * 5 + 4))
+8 + 7 + 2 + ((5 + 2) + 5 + 7 * 6 + (7 + 8 + 7 + 6 * 8 + 7) * (4 + 2 + 3 * 2 * 9))
+3 + ((7 * 6 * 2 * 9 + 3) * (7 * 8) * 2 * (3 * 5 + 8 * 3)) + 8 * 7 * 9 + 9
+2 + ((3 * 8 + 5 * 6) * 4) + 8 * 6 * (2 * 7 + 5 + 5 * (9 * 4 * 9)) * (4 + (2 * 6 * 5))
+(7 + 7 * (8 + 7) * (2 + 4 + 8 + 5 * 9 + 5)) * 7 + (4 * 2 + (7 + 8 * 4) + 9 * 3 + 4) * (7 * 7 + 2 + 7 + (8 + 8) + 9)
+(5 + 3) + 8 * (8 * 3 * 2 * 5) + 2 * 3 + 3
+((9 * 5 + 6 + 3 * 9) * (8 + 3 * 4 + 2 + 9 + 9) + 3) + 4 * 5 * 7 * (7 * (8 * 4 + 7)) + 6
+7 + 9 + 3 + (3 + (7 + 4 * 7 * 7) + (5 + 7) * 8 * (7 + 5 * 3 + 7 * 8))
+9 * (5 + 6 + 4 * (7 + 9 * 7 * 4) + 9) + (6 * 7) * (3 + 5 * (6 + 9 + 7)) + 8 * (5 * (2 + 3 + 6 + 8 * 8 * 9))
+2 * 6 + (3 + (6 * 3 * 6 + 2 * 8 + 5) * (5 + 7 * 8 * 4 + 4 + 7) * 2 * 8 + 3)
+6 + (7 * (3 + 2)) * 8 * 6
+8 * 7 * (8 * 7 * 8 + (4 + 4 + 4 + 3) + 4 * 8) + 7
+5 + 4 + (8 + 3 + 7 * 9 + 6 * 4) * (3 * 4 + 3 * 4 + 5) * 7 * 7
+6 * ((5 * 6 * 7) * (8 * 2 + 2 * 6 * 6 * 3) * (5 + 2) * 5 * (8 + 7 + 3)) * 3 * 7 * 9 * 6
+3 * 2 + (6 * 3 * 5 + 3) + 6 * 9 * 3
+(5 + 9 + (8 * 5 * 6 + 2 + 4 + 2)) + 9 * 9 + (7 + 9 * 7 * (8 * 6) + 2 + 5) + (9 + 4 * 7) * ((8 + 9 + 9 + 4) + (3 * 6) + 8 * 8 + (2 + 6))
+7 + 6 * (3 + 7) * 2
+(2 * 5 + 9 + 7 * 9) * 7 + 3 * 9 * 2
+((5 + 2 + 9 * 9 + 3 * 2) + 7 + 8 * 8) * 4 + (4 + 9 + 5 * 6 * 2 * (2 * 4 * 4 + 2)) + 9 + (9 + 4 * (8 * 7 * 8 * 3) * 8 * (2 * 9))
+(6 * 4 * 4) + 6 + 5 * 3 * 2
+(7 * 7) + 3 + ((4 * 8 + 3) * 2) + 5 + 5 * 3
+(3 + (8 + 6 * 4 + 7 * 7)) + (5 * 2 + (6 + 2 * 4 + 5) * 8) + ((6 * 4) * (3 + 8 + 8 * 6 + 8 + 4) + 6)
+9 * 3 + (8 * 2 * 8 + 6 * 7) * 5
+9 + 6 + (4 * 9) + ((2 + 2 + 7 + 2 * 6) * 3 * (2 * 6 + 9 * 4))
+6 * 8 + (3 * 3 + 9 + 4 * 3)
+2 * (4 + 2) * 8 + (2 * (6 * 6 * 9 * 5 * 6 + 8))
+6 * ((8 + 5 + 5 + 2 + 5) * 2 * (9 * 4 * 2 * 5 + 2 + 9)) + 3 * 3 * 7 + 4
+(6 * 7 + (8 * 7) + (8 * 7) * (9 + 6 + 9 + 2) + 6) + 7 * (8 + 7) + 7 + 6
+8 + 9 + (6 * 6 * 7 + 9 + 7) * (7 * (9 * 7 * 5 + 8) * 5 * (7 * 3) + 6 + 3) * ((5 + 5 * 7 * 7 * 5 * 9) + 9 * 6 + 5)
+2 * 9 + ((9 + 3) + 9 * (3 + 9 * 8 * 8 + 7 * 8) + 8 * 9) * 6 + 4 + 8

src/bin/homework.rs

@@ -0,0 +1,106 @@
+use advent2020::errors::TopLevelError;
+use advent2020::math::Math;
+use std::env;
+use std::fs;
+
+#[test]
+fn neutral_examples() {
+    assert_eq!(
+        71,
+        Math::new_neutral("1 + 2 * 3 + 4 * 5 + 6")
+            .unwrap()
+            .compute()
+    );
+    assert_eq!(
+        51,
+        Math::new_neutral("1 + (2 * 3) + (4 * (5 + 6))")
+            .unwrap()
+            .compute()
+    );
+    assert_eq!(26, Math::new_neutral("2 * 3 + (4 * 5)").unwrap().compute());
+    assert_eq!(
+        437,
+        Math::new_neutral("5 + (8 * 3 + 9 + 3 * 4 * 3)")
+            .unwrap()
+            .compute()
+    );
+    assert_eq!(
+        12240,
+        Math::new_neutral("5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4))")
+            .unwrap()
+            .compute()
+    );
+    assert_eq!(
+        13632,
+        Math::new_neutral("((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2")
+            .unwrap()
+            .compute()
+    );
+}
+
+#[test]
+fn add_first_examples() {
+    assert_eq!(
+        231,
+        Math::new_add_first("1 + 2 * 3 + 4 * 5 + 6")
+            .unwrap()
+            .compute()
+    );
+    assert_eq!(
+        51,
+        Math::new_add_first("1 + (2 * 3) + (4 * (5 + 6))")
+            .unwrap()
+            .compute()
+    );
+    assert_eq!(
+        46,
+        Math::new_add_first("2 * 3 + (4 * 5)").unwrap().compute()
+    );
+    assert_eq!(
+        1445,
+        Math::new_add_first("5 + (8 * 3 + 9 + 3 * 4 * 3)")
+            .unwrap()
+            .compute()
+    );
+    assert_eq!(
+        669060,
+        Math::new_add_first("5 * 9 * (7 * 3 * 3 + 9 * 3 + (8 + 6 * 4))")
+            .unwrap()
+            .compute()
+    );
+    assert_eq!(
+        23340,
+        Math::new_add_first("((2 + 4 * 9) * (6 + 9 * 8 + 6) + 6) + 2 + 4 * 2")
+            .unwrap()
+            .compute()
+    );
+}
+
+fn main() -> Result<(), TopLevelError> {
+    let filename = env::args().nth(1).expect("No file argument given.");
+    let contents = fs::read_to_string(filename)?;
+    let mut sum_neutral = 0;
+    let mut sum_add_first = 0;
+
+    for line in contents.lines() {
+        match Math::new_neutral(line) {
+            Ok(expr) => {
+                println!("{} ==> {}", line, expr.compute());
+                sum_neutral += expr.compute();
+            }
+            Err(e) => println!("PARSE ERROR: {}", e),
+        }
+        match Math::new_add_first(line) {
+            Ok(expr) => {
+                println!("{} ==> {}", line, expr.compute());
+                sum_add_first += expr.compute();
+            }
+            Err(e) => println!("PARSE ERROR: {}", e),
+        }
+    }
+
+    println!("Total (neutral ordering): {}", sum_neutral);
+    println!("Total (add-first ordering): {}", sum_add_first);
+
+    Ok(())
+}

src/lib.rs

@@ -1,2 +1,5 @@
+extern crate lalrpop_util;
+
 pub mod errors;
 pub mod map;
+pub mod math;

src/math.rs

@@ -0,0 +1,16 @@
+mod ast;
+
+lalrpop_util::lalrpop_mod!(parse, "/math/parse.rs");
+
+pub use crate::math::ast::Math;
+use crate::math::parse::{ExprMulParser, ExprParser};
+
+impl Math {
+    pub fn new_neutral(s: &str) -> Result<Math, String> {
+        ExprParser::new().parse(s).map_err(|x| format!("{}", x))
+    }
+
+    pub fn new_add_first(s: &str) -> Result<Math, String> {
+        ExprMulParser::new().parse(s).map_err(|x| format!("{}", x))
+    }
+}

src/math/ast.rs

@@ -0,0 +1,15 @@
+pub enum Math {
+    Constant(usize),
+    Multiply(Box<Math>, Box<Math>),
+    Add(Box<Math>, Box<Math>),
+}
+
+impl Math {
+    pub fn compute(&self) -> usize {
+        match self {
+            Math::Constant(x) => *x,
+            Math::Multiply(a, b) => a.compute() * b.compute(),
+            Math::Add(a, b) => a.compute() + b.compute(),
+        }
+    }
+}

src/math/parse.lalrpop

@@ -0,0 +1,32 @@
+use crate::math::ast::Math;
+use std::str::FromStr;
+
+grammar;
+
+pub Expr: Math = {
+    <e1: Expr> "+" <e2: Term> => Math::Add(Box::new(e1), Box::new(e2)),
+    <e1: Expr> "*" <e2: Term> => Math::Multiply(Box::new(e1), Box::new(e2)),
+    <e: Term> => e,
+} 
+
+Term: Math = {
+    <n:Num> => Math::Constant(n),
+    "(" <t:Expr> ")" => t,
+};
+
+pub ExprMul: Math = {
+    <e1: ExprMul> "*" <e2: ExprAdd> => Math::Multiply(Box::new(e1), Box::new(e2)),
+    <e: ExprAdd> => e,
+}
+
+ExprAdd: Math = {
+    <e1: ExprAdd> "+" <e2: ExprConst> => Math::Add(Box::new(e1), Box::new(e2)),
+    <e: ExprConst> => e,
+}
+
+ExprConst: Math = {
+    <n:Num> => Math::Constant(n),
+    "(" <t:ExprMul> ")" => t,
+}
+
+Num: usize = <s:r"[0-9]+"> => usize::from_str(s).unwrap();