348. Design Tic-Tac-Toe π
Description
Assume the following rules are for the tic-tac-toe game on an n x n
board between two players:
- A move is guaranteed to be valid and is placed on an empty block.
- Once a winning condition is reached, no more moves are allowed.
- A player who succeeds in placing
n
of their marks in a horizontal, vertical, or diagonal row wins the game.
Implement the TicTacToe
class:
TicTacToe(int n)
Initializes the object the size of the boardn
.int move(int row, int col, int player)
Indicates that the player with idplayer
plays at the cell(row, col)
of the board. The move is guaranteed to be a valid move, and the two players alternate in making moves. Return0
if there is no winner after the move,1
if player 1 is the winner after the move, or2
if player 2 is the winner after the move.
Example 1:
Input ["TicTacToe", "move", "move", "move", "move", "move", "move", "move"] [[3], [0, 0, 1], [0, 2, 2], [2, 2, 1], [1, 1, 2], [2, 0, 1], [1, 0, 2], [2, 1, 1]] Output [null, 0, 0, 0, 0, 0, 0, 1] Explanation TicTacToe ticTacToe = new TicTacToe(3); Assume that player 1 is "X" and player 2 is "O" in the board. ticTacToe.move(0, 0, 1); // return 0 (no one wins) |X| | | | | | | // Player 1 makes a move at (0, 0). | | | | ticTacToe.move(0, 2, 2); // return 0 (no one wins) |X| |O| | | | | // Player 2 makes a move at (0, 2). | | | | ticTacToe.move(2, 2, 1); // return 0 (no one wins) |X| |O| | | | | // Player 1 makes a move at (2, 2). | | |X| ticTacToe.move(1, 1, 2); // return 0 (no one wins) |X| |O| | |O| | // Player 2 makes a move at (1, 1). | | |X| ticTacToe.move(2, 0, 1); // return 0 (no one wins) |X| |O| | |O| | // Player 1 makes a move at (2, 0). |X| |X| ticTacToe.move(1, 0, 2); // return 0 (no one wins) |X| |O| |O|O| | // Player 2 makes a move at (1, 0). |X| |X| ticTacToe.move(2, 1, 1); // return 1 (player 1 wins) |X| |O| |O|O| | // Player 1 makes a move at (2, 1). |X|X|X|
Constraints:
2 <= n <= 100
- player is
1
or2
. 0 <= row, col < n
(row, col)
are unique for each different call tomove
.- At most
n2
calls will be made tomove
.
Follow-up: Could you do better than O(n2)
per move()
operation?
Solutions
Solution 1: Counting
We can use an array of length $n \times 2 + 2$ to record the number of pieces each player has in each row, each column, and the two diagonals. We need two such arrays to record the number of pieces for the two players respectively.
When a player has $n$ pieces in a certain row, column, or diagonal, that player wins.
In terms of time complexity, the time complexity of each move is $O(1)$. The space complexity is $O(n)$, where $n$ is the length of the side of the chessboard.
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