Design an algorithm to figure out if someone has won a game of tic-tac-toe. Input is a string array of size N x N, including characters " ", "X" and "O", where " " represents a empty grid.
The rules of tic-tac-toe are as follows:
- Players place characters into an empty grid(" ") in turn.
- The first player always place character "O", and the second one place "X".
- Players are only allowed to place characters in empty grid. Replacing a character is not allowed.
- If there is any row, column or diagonal filled with N same characters, the game ends. The player who place the last charater wins.
- When there is no empty grid, the game ends.
- If the game ends, players cannot place any character further.
If there is any winner, return the character that the winner used. If there's a draw, return "Draw". If the game doesn't end and there is no winner, return "Pending".
Example 1:
Input: board = ["O X"," XO","X O"] Output: "X"
Example 2:
Input: board = ["OOX","XXO","OXO"] Output: "Draw" Explanation: no player wins and no empty grid left
Example 3:
Input: board = ["OOX","XXO","OX "] Output: "Pending" Explanation: no player wins but there is still a empty grid
Note:
1 <= board.length == board[i].length <= 100- Input follows the rules.