Day 6 done

Author: BakerNet

README.md

@@ -10,7 +10,7 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 
 | Year | Completed |
 | :---: | :---: |
-| [2025](aoc2025) | 10/24 |
+| [2025](aoc2025) | 12/24 |
 | [2024](aoc2024) | 50/50 |
 | [2023](aoc2023) | 50/50 |
 

aoc2025/README.md

@@ -11,7 +11,7 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 3](https://adventofcode.com/2025/day/3) | [code](src/bin/03.rs) | ⭐ | ⭐ |
 | [Day 4](https://adventofcode.com/2025/day/4) | [code](src/bin/04.rs) | ⭐ | ⭐ |
 | [Day 5](https://adventofcode.com/2025/day/5) | [code](src/bin/05.rs) | ⭐ | ⭐ |
-| [Day 6](https://adventofcode.com/2025/day/6) | [code](src/bin/06.rs) | _ | _ |
+| [Day 6](https://adventofcode.com/2025/day/6) | [code](src/bin/06.rs) | ⭐ | ⭐ |
 | [Day 7](https://adventofcode.com/2025/day/7) | [code](src/bin/07.rs) | _ | _ |
 | [Day 8](https://adventofcode.com/2025/day/8) | [code](src/bin/08.rs) | _ | _ |
 | [Day 9](https://adventofcode.com/2025/day/9) | [code](src/bin/09.rs) | _ | _ |

aoc2025/data/examples/06.txt

@@ -0,0 +1,4 @@
+123 328  51 64 
+ 45 64  387 23 
+  6 98  215 314
+*   +   *   + 

aoc2025/src/bin/06.rs

@@ -0,0 +1,98 @@
+use itertools::Itertools;
+
+advent_of_code::solution!(6);
+
+fn split_input(input: &str) -> (&str, Vec<&str>) {
+    let lines = input.lines().collect_vec();
+    // trim because of part 2 final coumn width calculation
+    let ops_line = &lines[lines.len() - 1].trim();
+    let num_lines = lines[..lines.len() - 1].to_vec();
+    (ops_line, num_lines)
+}
+
+fn calc_total(ops: &[&str], nums: &[Vec<u64>]) -> u64 {
+    nums.iter()
+        .enumerate()
+        .fold(vec![0; ops.len()], |mut totals, (i, v)| {
+            let t = &mut totals[i];
+            v.iter().for_each(|x| match ops[i] {
+                _ if *t == 0 => *t = *x,
+                "*" => *t *= *x,
+                "+" => *t += *x,
+                other => panic!("Should exist: {}", other),
+            });
+            totals
+        })
+        .iter()
+        .sum()
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let (ops_line, num_lines) = split_input(input);
+    let ops = ops_line.split_whitespace().collect_vec();
+    let ops_count = ops.len();
+    let mut nums = vec![vec![0; num_lines.len()]; ops_count];
+    num_lines.iter().enumerate().for_each(|(i, &s)| {
+        s.split_whitespace()
+            .enumerate()
+            .for_each(|(col, x)| nums[col][i] = x.parse::<u64>().expect("should be ints"))
+    });
+    Some(calc_total(&ops, &nums))
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let (ops_line, num_lines) = split_input(input);
+    let ops = ops_line.split_whitespace().collect_vec();
+    let ops_count = ops.len();
+    let mut col_numbers = vec![0; ops_count];
+    // each op is the first index in the number column for its set of numbers
+    // use this to get the count of columns (numbers) in the number column
+    ops_line.chars().skip(1).fold(0, |col, c| match c {
+        '*' | '+' => col + 1,
+        ' ' => {
+            col_numbers[col] += 1;
+            col
+        }
+        other => panic!("Shouldn't exist: {}", other),
+    });
+    // last col_width can't be known from ops row alone
+    let max_width = num_lines
+        .iter()
+        .map(|s| s.len())
+        .max()
+        .expect("Sum should exist");
+    col_numbers[ops_count - 1] = max_width - ops_line.len() + 1;
+
+    let mut nums = col_numbers.iter().map(|x| vec![0; *x]).collect_vec();
+    num_lines.iter().for_each(|&s| {
+        s.chars().fold((0, 0), |(col_idx, number_idx), c| {
+            if number_idx >= col_numbers[col_idx] {
+                // we are in-between number columns
+                return (col_idx + 1, 0);
+            }
+            let update_num = &mut nums[col_idx][number_idx];
+            if let Some(x) = c.to_digit(10) {
+                *update_num = *update_num * 10 + x as u64;
+            }
+            (col_idx, number_idx + 1)
+        });
+    });
+    Some(calc_total(&ops, &nums))
+}
+
+#[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(4277556));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(3263827));
+    }
+}