From 161ba78efe779454aedf8321163df30c0a4d2005 Mon Sep 17 00:00:00 2001
From: Timo Schneider <timoschneider04@gmail.com>
Date: Tue, 9 Dec 2025 21:13:37 +0100
Subject: [PATCH] finished day04

---
 README.md            | 22 +++++++--------
 src/day04/common.rs  | 64 ++++++++++++++++++++++++++++++++++++++++++++
 src/day04/mod.rs     |  2 +-
 src/day04/part04a.rs | 47 ++------------------------------
 src/day04/part04b.rs | 10 ++++++-
 5 files changed, 87 insertions(+), 58 deletions(-)
 create mode 100644 src/day04/common.rs

diff --git a/README.md b/README.md
index 9ad2b5d..eba34ac 100644
--- a/README.md
+++ b/README.md
@@ -1,23 +1,23 @@
 # Advent of Code 2025
 ```bash
-day01:A =>            1150  (    52us)
-day01:B =>            1150  (    50us)
-day02:A =>     31839939622  (  9337us)
-day02:B =>     41662374059  ( 68756us)
+day01:A =>            1150  (    50us)
+day01:B =>            1150  (    48us)
+day02:A =>     31839939622  (  7730us)
+day02:B =>     41662374059  ( 64909us)
 day03:A =>           16812  (    83us)
-day03:B => 166345822896410  (   292us)
-day04:A =>            1518  (   190us)
-day04:B =>               0  (     0us)
+day03:B => 166345822896410  (   285us)
+day04:A =>            1518  (   194us)
+day04:B =>            8665  (  3753us)
 day05:A =>               0  (     0us)
 day05:B =>               0  (     0us)
-day06:A =>   6503327062445  (   201us)
-day06:B =>   9640641878593  (   135us)
+day06:A =>   6503327062445  (   196us)
+day06:B =>   9640641878593  (   134us)
 day07:A =>               0  (     0us)
 day07:B =>               0  (     0us)
 day08:A =>               0  (     0us)
 day08:B =>               0  (     0us)
-day09:A =>      4725826296  (   160us)
+day09:A =>      4725826296  (   165us)
 day09:B =>               0  (     0us)
                             ----------
-                              81842us
+                              78131us
 ```
\ No newline at end of file
diff --git a/src/day04/common.rs b/src/day04/common.rs
new file mode 100644
index 0000000..306982f
--- /dev/null
+++ b/src/day04/common.rs
@@ -0,0 +1,64 @@
+
+pub fn parse_to_floor(input: String) -> Vec<Vec<u8>> {
+    let mut rows: Vec<Vec<u8>> = Vec::with_capacity(input.len() + 2);
+    rows.push(vec![0u8; input.len()]);
+    rows.append(
+        &mut input
+            .lines()
+            .map(|line| {
+                let mut col: Vec<u8> = Vec::with_capacity(line.len() + 2);
+                col.push(0u8);
+                col.append(
+                    &mut line
+                        .chars()
+                        .map(|c| match c {
+                            '@' => 1u8,
+                            _ => 0u8,
+                        })
+                        .collect(),
+                );
+                col.push(0u8);
+                col
+            })
+            .collect(),
+    );
+    rows.push(vec![0u8; input.len()]);
+
+    rows
+}
+
+pub fn remove_if_possible(floor: &mut Vec<Vec<u8>>) -> Option<u64> {
+    let mut removed: Vec<(usize, usize)> = Vec::new();
+
+    floor
+        .windows(3)
+        .enumerate()
+        .for_each(|(r, rows)| {
+            rows[0]
+                .iter()
+                .zip(rows[1].iter())
+                .zip(rows[2].iter())
+                .map(|((a, b), c)| (a, b, c))
+                .collect::<Vec<(&u8, &u8, &u8)>>()
+                .windows(3)
+                .enumerate()
+                .for_each(|(c, cols)| {
+                    if cols[1].1 == &0u8 {
+                        return;
+                    }
+                    if cols.iter().map(|(a, b, c)| *a + *b + *c).sum::<u8>() - 1 < 4 {
+                        removed.push((r+1, c+1));
+                    }
+                });
+        });
+
+    removed.iter().for_each(|(r, c)| {
+        floor[*r][*c] = 0;
+    });
+
+    if removed.len() == 0 {
+        return None;
+    }
+
+    Some(removed.len() as u64)
+}
\ No newline at end of file
diff --git a/src/day04/mod.rs b/src/day04/mod.rs
index 9978634..69252e6 100644
--- a/src/day04/mod.rs
+++ b/src/day04/mod.rs
@@ -1,5 +1,6 @@
 pub mod part04a;
 pub mod part04b;
+mod common;
 
 #[cfg(test)]
 mod tests {
@@ -22,7 +23,6 @@ mod tests {
     }
 
     #[test]
-    #[ignore]
     fn part04b() {
         assert_eq!(part04b::solve(PUZZLE.to_string()), 43);
     }
diff --git a/src/day04/part04a.rs b/src/day04/part04a.rs
index a7130b0..4dc585f 100644
--- a/src/day04/part04a.rs
+++ b/src/day04/part04a.rs
@@ -1,48 +1,5 @@
+use crate::day04::common::{parse_to_floor, remove_if_possible};
 
 pub fn solve(puzzle: String) -> u64 {
-    let mut solution: u64 = 0;
-
-    let mut rows: Vec<Vec<u8>> = Vec::with_capacity(puzzle.len() + 2);
-    rows.push(vec![0u8; puzzle.len()]);
-    rows.append(
-        &mut puzzle
-            .lines()
-            .map(|line| {
-                let mut col: Vec<u8> = Vec::with_capacity(line.len() + 2);
-                col.push(0u8);
-                col.append(
-                    &mut line
-                        .chars()
-                        .map(|c| match c {
-                            '@' => 1u8,
-                            _ => 0u8,
-                        })
-                        .collect(),
-                );
-                col.push(0u8);
-                col
-            })
-            .collect(),
-    );
-    rows.push(vec![0u8; puzzle.len()]);
-
-    rows.windows(3).for_each(|rows| {
-        rows[0]
-            .iter()
-            .zip(rows[1].iter())
-            .zip(rows[2].iter())
-            .map(|((a, b), c)| (*a, *b, *c))
-            .collect::<Vec<(u8, u8, u8)>>()
-            .windows(3)
-            .for_each(|cols| {
-                if cols[1].1 != 1u8 {
-                    return;
-                }
-                if cols.iter().map(|(a, b, c)| *a + *b + *c).sum::<u8>() - 1 < 4 {
-                    solution += 1;
-                }
-            });
-    });
-
-    solution
+    remove_if_possible(&mut parse_to_floor(puzzle)).unwrap_or_else(|| 0)
 }
diff --git a/src/day04/part04b.rs b/src/day04/part04b.rs
index 10fe1d8..0bc78cf 100644
--- a/src/day04/part04b.rs
+++ b/src/day04/part04b.rs
@@ -1,6 +1,14 @@
+use crate::day04::common::{parse_to_floor, remove_if_possible};
 
 pub fn solve(puzzle: String) -> u64 {
-    0 // TODO
+    let mut solution: u64 = 0;
+    let mut floor = parse_to_floor(puzzle);
+
+    while let Some(removed) = remove_if_possible(&mut floor) {
+        solution += removed;
+    }
+
+    solution
 }