Day 7

Author: UnderscoreTud

README.md

@@ -27,9 +27,10 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 3](./src/bin/03.rs) | `561.0µs` | `565.5µs` |
 | [Day 4](./src/bin/04.rs) | `560.8µs` | `161.9µs` |
 | [Day 5](./src/bin/05.rs) | `344.6µs` | `323.6µs` |
-| [Day 6](./src/bin/06.rs) | `492.2µs` | `118.9ms` |
+| [Day 6](./src/bin/06.rs) | `488.0µs` | `119.9ms` |
+| [Day 7](./src/bin/07.rs) | `186.7µs` | `101.6ms` |
 
-**Total: 122.70ms**
+**Total: 225.49ms**
 <!--- benchmarking table --->
 
 ---

data/examples/07.txt

@@ -0,0 +1,9 @@
+190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20

src/bin/07.rs

@@ -0,0 +1,75 @@
+use rayon::iter::ParallelIterator;
+use itertools::Itertools;
+use rayon::prelude::ParallelString;
+
+advent_of_code::solution!(7);
+
+fn parse_and_solve<F>(input: &str, equation_checker: F) -> u64
+    where F: Fn(&u64, &[u64], &u64) -> bool + Sync
+{
+    input.par_lines()
+        .map(|line| {
+            let mut split = line.split_whitespace();
+            let Some(expected) = split.next() else { panic!() };
+            let expected = expected[0..expected.len() - 1].parse::<u64>().unwrap();
+            let terms = split.map(|num| num.parse::<u64>().unwrap()).collect_vec();
+            (terms, expected)
+        })
+        .filter_map(|(terms, expected)| {
+            if equation_checker(&terms[0], &terms[1..], &expected) { Some(expected) } else { None }
+        })
+        .sum()
+}
+
+fn is_valid_equation(current_term: &u64, terms: &[u64], expected: &u64) -> bool {
+    if terms.is_empty() {
+        return current_term == expected;
+    }
+
+    let next_term = terms[0];
+    let new_terms = &terms[1..];
+    [current_term * next_term, current_term + next_term].iter()
+        .filter(|term| *term <= expected)
+        .any(|term| is_valid_equation(term, new_terms, expected))
+}
+
+fn is_valid_equation_with_concat(current_term: &u64, terms: &[u64], expected: &u64) -> bool {
+    if terms.is_empty() {
+        return current_term == expected;
+    }
+
+    let next_term = terms[0];
+    let new_terms = &terms[1..];
+    [
+        current_term * next_term,
+        current_term + next_term,
+        (current_term.to_string() + &next_term.to_string()).parse().unwrap(),
+    ].iter()
+        .filter(|term| *term <= expected)
+        .any(|term| is_valid_equation_with_concat(term, new_terms, expected))
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    Some(parse_and_solve(input, is_valid_equation))
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    Some(parse_and_solve(input, is_valid_equation_with_concat))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(3749));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(11387));
+    }
+}