2021 day4/python: add solution

2021/day4/day4.py

@@ -0,0 +1,41 @@
+#!/usr/bin/env python
+
+import time
+
+import sys
+
+def board_won(board):
+    for row in board:
+        if all(x is None for x in row):
+            return True
+    for i in range(len(board[0])):
+        if all(row[i] is None for row in board):
+            return True
+    return False
+
+if __name__ == '__main__':
+    lines = [line.strip() for line in sys.stdin.readlines()]
+
+    draws = [int(n) for n in lines[0].split(',')]
+
+    boards = []
+    for i in range(2, len(lines), 6):
+        boards.append([[int(n) for n in line.split()] for line in lines[i:i+5]])
+
+    wins = []
+    for draw in draws:
+        for board_idx, board in enumerate(boards):
+            if board is None:
+                continue
+            for row in board:
+                try:
+                    idx = row.index(draw)
+                    row[idx] = None
+                except ValueError:
+                    pass
+            if board_won(board):
+                wins.append(draw * sum(n for row in board for n in row if n is not None))
+                boards[board_idx] = None
+
+    print(wins[0])
+    print(wins[-1])