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Author: vinija

1275-find-winner-on-a-tic-tac-toe-game/1275-find-winner-on-a-tic-tac-toe-game.py

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+class Solution:
+    def tictactoe(self, moves: List[List[int]]) -> str:
+
+        # Initialize the board, n = 3 in this problem.
+        n = 3
+        board = [[0] * n for _ in range(n)]
+        
+        # Check if any of 4 winning conditions to see if the current player has won.
+        def checkRow(row, player_id):
+            for col in range(n):
+                if board[row][col] != player_id:
+                    return False
+            return True
+        
+        def checkCol(col, player_id):
+            for row in range(n):
+                if board[row][col] != player_id:
+                    return False
+            return True
+        
+        def checkDiagonal(player_id):
+            for row in range(n):
+                if board[row][row] != player_id:
+                    return False
+            return True
+        
+        def checkAntiDiagonal(player_id):
+            for row in range(n):
+                if board[row][n - 1 - row] != player_id:
+                    return False
+            return True
+        
+        # Start with player_1.
+        player = 1
+
+        for move in moves:
+            # extract 
+            row, col = move
+            board[row][col] = player
+            
+            # If any of the winning conditions is met, return the current player's id.
+            if checkRow(row, player) or checkCol(col, player) or \
+            (row == col and checkDiagonal(player)) or \
+            (row + col == n - 1 and checkAntiDiagonal(player)):
+                return 'A' if player == 1 else 'B'
+            
+            # If no one wins so far, change to the other player alternatively. 
+            # That is from 1 to -1, from -1 to 1.
+            player *= -1
+            
+        # If all moves are completed and there is still no result, we shall check if
+        # the grid is full or not. If so, the game ends with draw, otherwise pending.    
+        return "Draw" if len(moves) == n * n else "Pending"