From 8a3ec2f2f1b5d8402d296014848d9626e44904ee Mon Sep 17 00:00:00 2001
From: Julius de Jeu <julius@voidcorp.nl>
Date: Sat, 4 Dec 2021 10:12:56 +0100
Subject: [PATCH] Day 04 less mutable iterators

---
 src/day04.rs | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/src/day04.rs b/src/day04.rs
index 8c54df9..d7099bc 100644
--- a/src/day04.rs
+++ b/src/day04.rs
@@ -53,22 +53,19 @@ impl Day for Day04 {
 
     fn part2(&self) -> String {
         let z = self.clone();
-        let mut boards = z.boards.iter().cloned().map(Option::Some).collect::<Vec<Option<Board>>>();
+        let mut boards = z.boards;
         for number in z.numbers {
-            let some_count = boards.iter().map(|x| if x.is_some() { 1 } else { 0 }).sum::<u32>();
-            #[allow(clippy::manual_flatten)]
-            for boardd in &mut boards {
-                if let Some(board) = boardd {
-                    let res = board.mark(number);
-                    if res {
-                        if some_count == 1 {
-                            let s = board.unmarked_sum();
-                            return format!("{}", s * number);
-                        }
-                        *boardd = None;
+            let len = boards.len();
+            for board in &mut boards {
+                let res = board.mark(number);
+                if res {
+                    if len == 1 {
+                        let s = board.unmarked_sum();
+                        return format!("{}", s * number);
                     }
                 }
             }
+            boards = boards.iter().filter(|x| !x.complete()).cloned().collect();
         }
 
         panic!("no board can win?")
@@ -90,6 +87,10 @@ impl Board {
         self.check_rows() || self.check_columns()
     }
 
+    fn complete(&self) -> bool {
+        self.check_rows() || self.check_columns()
+    }
+
     fn check_rows(&self) -> bool {
         for columns in &self.0 {
             if columns.iter().all(Option::is_none) {