From 93cca2e13567879cc880046ebd066ac891e32064 Mon Sep 17 00:00:00 2001
From: Jan Doumont <jan@6a616e.net>
Date: Mon, 8 Dec 2025 02:12:51 +0100
Subject: [PATCH] day6

---
 src/day6.rs | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/lib.rs  |   3 +-
 2 files changed, 131 insertions(+), 1 deletion(-)
 create mode 100644 src/day6.rs

diff --git a/src/day6.rs b/src/day6.rs
new file mode 100644
index 0000000..faf4d53
--- /dev/null
+++ b/src/day6.rs
@@ -0,0 +1,129 @@
+#[aoc(day6, part1)]
+pub fn part1(input: &str) -> u64 {
+    let (nums_rows, ops) = parse_input(input);
+    let nums_cols = transpose_nums(&nums_rows);
+    ops.iter()
+        .zip(nums_cols)
+        .map(|(op, nums)| match op {
+            Operator::Add => nums.iter().sum(),
+            Operator::Mult => nums.iter().fold(1, |x, y| x * y),
+        })
+        .sum()
+}
+
+#[aoc(day6, part2)]
+pub fn part2(input: &str) -> u64 {
+    let (nums, ops) = parse_input_2(input);
+    ops.iter()
+        .zip(nums)
+        .map(|(op, nums)| match op {
+            Operator::Add => nums.iter().sum(),
+            Operator::Mult => nums.iter().fold(1, |x, y| x * y),
+        })
+        .sum()
+}
+#[derive(Debug)]
+enum Operator {
+    Add,
+    Mult,
+}
+
+fn parse_input(input: &str) -> (Vec<Vec<u64>>, Vec<Operator>) {
+    (
+        input
+            .lines()
+            .take_while(|l| l.trim_ascii_start().chars().next().unwrap().is_digit(10))
+            .map(|l| {
+                {
+                    l.split_ascii_whitespace()
+                        .map(|x| x.parse::<u64>().unwrap())
+                        .collect::<Vec<u64>>()
+                }
+            })
+            .collect(),
+        input
+            .lines()
+            .last()
+            .unwrap()
+            .split_whitespace()
+            .map(|x| match x {
+                "+" => Operator::Add,
+                "*" => Operator::Mult,
+                _ => panic!("Undefined operation {}", x),
+            })
+            .collect(),
+    )
+}
+
+fn parse_input_2(input: &str) -> (Vec<Vec<u64>>, Vec<Operator>) {
+    let n = input.lines().count() - 1;
+    let m_chars = input.lines().next().unwrap().chars().count();
+    let mut char_cols = vec![Vec::with_capacity(n); m_chars];
+
+    for (i, line) in input.lines().take(n).enumerate() {
+        for (j, char) in line.chars().enumerate() {
+            char_cols[j].insert(i, char);
+        }
+    }
+
+    let ops: Vec<Operator> = input
+        .lines()
+        .last()
+        .unwrap()
+        .split_whitespace()
+        .map(|x| match x {
+            "+" => Operator::Add,
+            "*" => Operator::Mult,
+            _ => panic!("Undefined operation {}", x),
+        })
+        .collect();
+
+    let mut nums: Vec<Vec<u64>> = vec![Vec::new(); ops.len()];
+
+    let mut op_counter = 0;
+    for col in char_cols {
+        let numstr = col.iter().collect::<String>();
+        if numstr.trim().is_empty() {
+            op_counter = op_counter + 1;
+        } else {
+            nums[op_counter].push(numstr.trim().parse::<u64>().unwrap_or(0));
+        }
+    }
+
+    assert_eq!(ops.len(), nums.len());
+    (nums, ops)
+}
+
+fn transpose_nums(nums: &Vec<Vec<u64>>) -> Vec<Vec<u64>> {
+    let n = nums.len();
+    let m = nums[0].len();
+    let mut columns = vec![Vec::with_capacity(n); m];
+    for (i, line) in nums.iter().enumerate() {
+        for (j, num) in line.iter().enumerate() {
+            columns[j].insert(i, *num);
+        }
+    }
+    columns
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const EXAMPLE_INPUT: &str = "\
+123 328  51 64 
+ 45 64  387 23 
+  6 98  215 314
+*   +   *   +  
+";
+
+    #[test]
+    fn test_part1() {
+        assert_eq!(part1(EXAMPLE_INPUT), 4277556);
+    }
+
+    #[test]
+    fn test_part2() {
+        assert_eq!(part2(EXAMPLE_INPUT), 3263827);
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index c7ba38e..10f8ffb 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,6 +7,7 @@ extern crate aoc_runner_derive;
 // pub mod day2;
 // pub mod day3;
 // pub mod day4;
-pub mod day5;
+// pub mod day5;
+pub mod day6;
 
 aoc_lib! { year = 2025 }