7th day

Author: majcn

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 +1,79 @@
+advent_of_code::solution!(7);
+
+use advent_of_code::maneatingape::parse::*;
+
+fn parse_data(input: &str) -> Vec<Vec<u64>> {
+    input
+        .lines()
+        .map(|line| line.iter_unsigned().collect())
+        .collect()
+}
+
+fn solve(result: u64, left: u64, right: &[u64], use_concatenation: bool) -> bool {
+    if right.is_empty() {
+        return result == left;
+    }
+
+    if left > result {
+        return false;
+    }
+
+    let first_left_value = left + right[0];
+    if solve(result, first_left_value, &right[1..], use_concatenation) {
+        return true;
+    }
+
+    let second_left_value = left * right[0];
+    if solve(result, second_left_value, &right[1..], use_concatenation) {
+        return true;
+    }
+
+    if use_concatenation {
+        let third_left_number = left * 10_u64.pow(right[0].ilog(10) + 1) + right[0];
+        if solve(result, third_left_number, &right[1..], use_concatenation) {
+            return true;
+        }
+    }
+
+    false
+}
+
+fn part_x(data: Vec<Vec<u64>>, use_concatenation: bool) -> u64 {
+    data.into_iter()
+        .filter(|line| solve(line[0], line[1], &line[2..], use_concatenation))
+        .map(|line| line[0])
+        .sum()
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let data = parse_data(input);
+
+    let result = part_x(data, false);
+
+    Some(result)
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let data = parse_data(input);
+
+    let result = part_x(data, true);
+
+    Some(result)
+}
+
+#[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));
+    }
+}