Generify day 19 over all pattern vectors

2020/src/bin/day19.rs

@@ -3,18 +3,14 @@ extern crate test;
 use aoc2020::common::*;
 use itertools::Itertools;
 
-#[derive(Debug, PartialEq, Clone, Copy)]
+#[derive(Debug, PartialEq, Clone)]
 enum Rule {
     Char(u8),
-    And((usize, usize)),
-    AndOr((usize, usize), (usize, usize)),
-    Or((usize, usize)),
+    And(Vec<usize>),
+    AndOr(Vec<usize>, Vec<usize>),
+    Any(Vec<usize>),
     Useless(usize), // just delegates to another rule and makes parsing annoying
-    // This is why you don’t change the requirements once the implementation is done. REEEEEE
-    Special8(usize, (usize, usize)),
-    Special11((usize, usize), (usize, usize, usize)),
-    // If Rule was a recursive struct, this could have been defined as And(first, And(second, third)), but alas
-    Triple((usize, usize, usize)),
+    Either(Vec<usize>, Vec<usize>),
 }
 
 type Parsed<'a> = (RuleSet, &'a str);
@@ -23,40 +19,38 @@ type Parsed<'a> = (RuleSet, &'a str);
 struct RuleSet(Vec<Rule>);
 
 impl RuleSet {
+    fn and_combinations(&self, s: &str, rules: &[usize], start: usize) -> Vec<usize> {
+        if let Some(&rule) = rules.first() {
+            if s.len() <= start {
+                return vec![];
+            }
+            self.matches(&s[start..], self.0[rule].clone())
+                .into_iter()
+                .flat_map(|i| self.and_combinations(s, &rules[1..], start + i).into_iter())
+                .collect()
+        } else {
+            vec![start]
+        }
+    }
+
     fn matches(&self, s: &str, rule: Rule) -> Vec<usize> {
         if s.len() == 0 {
             return vec![];
         }
         match rule {
             Rule::Char(c) => (s.as_bytes().first() == Some(&c)).then(|| vec![1]).unwrap_or_else(Vec::new),
-            Rule::And((r1, r2)) => self
-                .matches(s, self.0[r1])
+            Rule::And(v) => self.and_combinations(s, v.as_slice(), 0),
+            Rule::AndOr(v1, v2) => self
+                .matches(s, Rule::And(v1))
                 .into_iter()
-                .flat_map(|i| self.matches(&s[i..], self.0[r2]).into_iter().map(move |j| i + j))
+                .chain(self.matches(s, Rule::And(v2)))
                 .collect(),
-            Rule::AndOr((r1, r2), (r3, r4)) => self
-                .matches(s, Rule::And((r1, r2)))
-                .into_iter()
-                .chain(self.matches(s, Rule::And((r3, r4))))
-                .collect(),
-            Rule::Or((r1, r2)) => self.matches(s, self.0[r1]).into_iter().chain(self.matches(s, self.0[r2])).collect(),
-            Rule::Useless(r) => self.matches(s, self.0[r]),
-            // part 2 shit below:
-            Rule::Special8(first, second) => self
-                .matches(s, self.0[first])
-                .into_iter()
-                .chain(self.matches(s, Rule::And(second)))
-                .collect(),
-            Rule::Special11(first, second) => self
+            Rule::Any(v) => v.into_iter().flat_map(|r| self.matches(s, self.0[r].clone())).collect(),
+            Rule::Useless(r) => self.matches(s, self.0[r].clone()),
+            Rule::Either(first, second) => self
                 .matches(s, Rule::And(first))
                 .into_iter()
-                .chain(self.matches(s, Rule::Triple(second)))
-                .collect(),
-            Rule::Triple((r1, r2, r3)) => self
-                .matches(s, self.0[r1])
-                .into_iter()
-                .flat_map(|i| self.matches(&s[i..], self.0[r2]).into_iter().map(move |j| i + j))
-                .flat_map(|i| self.matches(&s[i..], self.0[r3]).into_iter().map(move |j| i + j))
+                .chain(self.matches(s, Rule::And(second)))
                 .collect(),
         }
     }
@@ -80,12 +74,12 @@ fn parse_input<'a>(raw: &'a str) -> Parsed<'a> {
                     split
                         .clone()
                         .next_tuple()
-                        .map(|(a, b, c, d)| Rule::AndOr((a, b), (c, d)))
-                        .or_else(|| split.next_tuple().map(|(a, b)| Rule::Or((a, b))))
+                        .map(|(a, b, c, d)| Rule::AndOr(vec![a, b], vec![c, d]))
+                        .or_else(|| split.next_tuple().map(|(a, b)| Rule::Any(vec![a, b])))
                         .unwrap()
                 }
                 chr if chr.contains('"') => Rule::Char(chr.bytes().skip_while(|&b| b != b'"').skip(1).next().unwrap()),
-                and if and.contains(' ') => Rule::And(and.split(' ').map(|s| s.parse().unwrap()).next_tuple().unwrap()),
+                and if and.contains(' ') => Rule::And(and.split(' ').map(|s| s.parse().unwrap()).collect()),
                 useless => Rule::Useless(useless.parse().unwrap()),
             })
             .collect(),
@@ -94,15 +88,21 @@ fn parse_input<'a>(raw: &'a str) -> Parsed<'a> {
 }
 
 fn part1((rules, input): &Parsed) -> usize {
-    input.lines().filter(|l| rules.matches(l, rules.0[0]).contains(&l.len())).count()
+    input
+        .lines()
+        .filter(|l| rules.matches(l, rules.0[0].clone()).contains(&l.len()))
+        .count()
 }
 
 fn part2(parsed: &Parsed) -> usize {
     let mut rules = parsed.0.clone();
-    rules.0[8] = Rule::Special8(42, (42, 8));
-    rules.0[11] = Rule::Special11((42, 31), (42, 11, 31));
-    dbg!(parsed.1.lines().map(|l| (l, rules.matches(l, rules.0[0]))).collect_vec());
-    parsed.1.lines().filter(|l| rules.matches(l, rules.0[0]).contains(&l.len())).count()
+    rules.0[8] = Rule::Either(vec![42], vec![42, 8]);
+    rules.0[11] = Rule::Either(vec![42, 31], vec![42, 11, 31]);
+    parsed
+        .1
+        .lines()
+        .filter(|l| rules.matches(l, rules.0[0].clone()).contains(&l.len()))
+        .count()
 }
 
 fn main() {