From dc1725a103c5c61017b9eddc3d5f3d42daaf7e78 Mon Sep 17 00:00:00 2001
From: Steph <noreply+steph@code.steph.tools>
Date: Thu, 1 Dec 2022 21:02:00 +0100
Subject: [PATCH] Day 4 part 2 done in Rust!

---
 2021/4/src/main.rs | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/2021/4/src/main.rs b/2021/4/src/main.rs
index 15791af..9e43faf 100644
--- a/2021/4/src/main.rs
+++ b/2021/4/src/main.rs
@@ -1,4 +1,5 @@
 use std::fs;
+use std::collections::HashSet;
 
 fn main() {
     part_one();
@@ -105,6 +106,8 @@ fn part_two() {
         .collect()
     ).collect();
 
+    // Don't even ask okay, it works. I am a C programmer not a fp one :p
+    let mut last_winning_boards: Vec<(usize, Vec<Vec<i32>>)> = vec![];
     for num in bingo_nums {
         boards = boards
             .into_iter()
@@ -119,8 +122,8 @@ fn part_two() {
             )
             .collect();
 
-        let winning_boards: Vec<&Vec<Vec<i32>>> = boards.iter()
-            .filter(|board|
+        let winning_boards: Vec<(usize, Vec<Vec<i32>>)> = boards.iter().cloned().enumerate()
+            .filter(|(i, board)|
                 board.iter().filter(|row|
                     row[0] == -1 && row[1] == -1 && row[2] == -1 && row[3] == -1 && row[4] == -1
                 ).collect::<Vec<&Vec<i32>>>().len() > 0 ||
@@ -130,9 +133,14 @@ fn part_two() {
             ).collect();
 
         if winning_boards.len() == boards.len() {
-            let sum: i32 = winning_boards.into_iter().last().into_iter().flatten().flatten().filter(|x| **x != -1).sum();
-            println!("Part 2, final score: {}", sum * num);
+            let new_nums: HashSet<usize> = winning_boards.iter().map(|(i, x)| i).cloned().collect();
+            let old_nums: HashSet<usize> = last_winning_boards.iter().map(|(i, x)| i).cloned().collect();
+            let that_one_fucker: HashSet<usize> = &new_nums - &old_nums;
+            let sum: i32 = winning_boards.get(that_one_fucker.iter().next().unwrap().clone()).unwrap().clone().1.into_iter().flatten().filter(|x| *x != -1).sum();
+            println!("Part 2, final score: {:?}", sum * num);
             break;
         }
+
+        last_winning_boards = winning_boards;
     }
 }