From b2a89160ebe6e8ea5222c77a7416930dc332e949 Mon Sep 17 00:00:00 2001
From: Tomasz Kramkowski <tk@the-tk.com>
Date: Sat, 4 Dec 2021 13:16:18 +0000
Subject: day 4: rewrite using better state tracking

---
 4.py | 68 +++++++++++++++++++++++++++++++++++++++++++-------------------------
 1 file changed, 43 insertions(+), 25 deletions(-)

diff --git a/4.py b/4.py
index b740d7b..5f15a8d 100644
--- a/4.py
+++ b/4.py
@@ -1,21 +1,44 @@
 from utils import open_day
-from dataclasses import dataclass
 
-@dataclass
-class Cell:
-    num: int
-    marked: bool = False
-
-Board = list[list[Cell]]
+class Board:
+    cells: list[int | None]
+    width: int
+    height: int
+    col_hits: list[int]
+    row_hits: list[int]
+    has_bingo: bool
+    unmarked_sum: int
+    def __init__(self, cells: list[list[int]]):
+        self.width = len(cells[0])
+        self.height = len(cells)
+        self.col_hits = [0 for _ in range(self.width)]
+        self.row_hits = [0 for _ in range(self.height)]
+        self.unmarked_sum = 0
+        self.cells = []
+        for row in cells:
+            for cell in row:
+                self.unmarked_sum += cell
+                self.cells.append(cell)
+        self.has_bingo = False
+    def check_bingo(self):
+        self.has_bingo = (
+            any(hits == self.height for hits in self.col_hits) or
+            any(hits == self.width for hits in self.row_hits)
+        )
+    def call(self, num: int):
+        for y in range(self.height):
+            for x in range(self.width):
+                cell = self.cells[x + self.width * y]
+                if cell == num:
+                    self.col_hits[x] += 1
+                    self.row_hits[y] += 1
+                    self.unmarked_sum -= cell
+                    self.check_bingo()
+                    return
+    @staticmethod
+    def from_string(s: str) -> 'Board':
+        return Board([[int(n) for n in l.split()] for l in s.split('\n')])
 
-def bingo(board: Board) -> bool:
-    for row in board:
-        if all(cell.marked for cell in row):
-            return True
-    for x in range(len(board[0])):
-        if all(board[y][x].marked for y in range(len(board))):
-            return True
-    return False
 
 def solve(nums: list[int], boards: list[Board]) -> tuple[int, int]:
     won: set[int] = set()
@@ -25,23 +48,18 @@ def solve(nums: list[int], boards: list[Board]) -> tuple[int, int]:
         i: int
         board: Board
         for i, board in enumerate(boards):
-            total = 0
-            for row in board:
-                for cell in row:
-                    if cell.num == num:
-                        cell.marked = True
-                    if not cell.marked:
-                        total += cell.num
-            if i not in won and bingo(board):
+            if i in won: continue
+            board.call(num)
+            if board.has_bingo:
                 won.add(i)
-                wins.append(num * total)
+                wins.append(num * board.unmarked_sum)
     return wins[0], wins[-1]
 
 nums: str | list[int]
 boards: list[str] | list[Board]
 nums, *boards = open_day(4).read().rstrip().split('\n\n')
 nums = list(map(int, nums.split(',')))
-boards = [[[Cell(int(n)) for n in l.split()] for l in b.split('\n')] for b in boards]
+boards = [Board.from_string(b) for b in boards]
 
 part1, part2 = solve(nums, boards)
 print(part1)
-- 
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