feat(06/2025): solve second part

Author: manhunto

readme.md

@@ -16,7 +16,7 @@
 | [Day 3: Lobby](src/solutions/year2025/day03.rs)               |   ⭐⭐   |            0.131 |            0.133 |
 | [Day 4: Printing Department](src/solutions/year2025/day04.rs) |   ⭐⭐   |            3.615 |            9.998 |
 | [Day 5: Cafeteria](src/solutions/year2025/day05.rs)           |   ⭐    |            0.275 |                - |
-| [Day 6: Trash Compactor](src/solutions/year2025/day06.rs)     |   ⭐    |            0.117 |                - |
+| [Day 6: Trash Compactor](src/solutions/year2025/day06.rs)     |   ⭐⭐   |            0.117 |            2.577 |
 
 # 2024
 

src/solutions/year2025/day06.rs

@@ -6,8 +6,8 @@ pub struct Day06;
 
 impl Solution for Day06 {
     fn part_one(&self, input: &str) -> String {
-        let (numbers, operations) = self.parse(input);
-        let column_count = numbers.first().unwrap().len();
+        let (numbers, operations) = self.parse_part_one(input);
+        let column_count = operations.len();
 
         (0..column_count)
             .map(|column| {
@@ -23,13 +23,28 @@ impl Solution for Day06 {
             .to_string()
     }
 
-    fn part_two(&self, _input: &str) -> String {
-        String::from("0")
+    fn part_two(&self, input: &str) -> String {
+        let (numbers, operations) = self.parse_part_two(input);
+
+        operations
+            .iter()
+            .rev()
+            .enumerate()
+            .map(|(column, operation)| {
+                let numbers_in_column = numbers.get(column).unwrap();
+
+                match operation {
+                    Operation::Add => numbers_in_column.iter().sum::<u64>(),
+                    Operation::Multiply => numbers_in_column.iter().product(),
+                }
+            })
+            .sum::<u64>()
+            .to_string()
     }
 }
 
 impl Day06 {
-    fn parse(&self, input: &str) -> (Vec<Vec<u64>>, Vec<Operation>) {
+    fn parse_part_one(&self, input: &str) -> (Vec<Vec<u64>>, Vec<Operation>) {
         let mut lines = input.lines().collect_vec();
         let operations_str = lines.pop().unwrap();
 
@@ -49,6 +64,40 @@ impl Day06 {
 
         (numbers, operations)
     }
+
+    fn parse_part_two(&self, input: &str) -> (Vec<Vec<u64>>, Vec<Operation>) {
+        let mut lines = input.lines().collect_vec();
+        let operations_str = lines.pop().unwrap();
+        let operations = operations_str
+            .split_whitespace()
+            .map(|x| x.parse::<Operation>().unwrap())
+            .collect_vec();
+
+        let column_width = operations_str.len();
+
+        let chunks = (0..column_width)
+            .rev()
+            .map(|column| {
+                lines
+                    .iter()
+                    .filter_map(|line| line.chars().nth(column))
+                    .filter(|ch| !ch.is_whitespace())
+                    .join("")
+                    .parse::<u64>()
+            })
+            .chunk_by(|x| x.is_err());
+
+        let mut groups = Vec::new();
+        for (_, rest) in &chunks {
+            let numbers = rest.flatten().collect_vec();
+
+            if !numbers.is_empty() {
+                groups.push(numbers);
+            }
+        }
+
+        (groups, operations)
+    }
 }
 
 #[derive(Debug)]
@@ -83,4 +132,9 @@ mod tests {
     fn part_one_example_test() {
         assert_eq!("4277556", Day06.part_one(EXAMPLE));
     }
+
+    #[test]
+    fn part_two_example_test() {
+        assert_eq!("3263827", Day06.part_two(EXAMPLE));
+    }
 }