[LeetCode] 348. Design Tic-Tac-Toe
Design a Tic-tac-toe game that is played between two players on a n x n grid.
You may assume the following rules:
- A move is guaranteed to be valid and is placed on an empty block.
- Once a winning condition is reached, no more moves is allowed.
- A player who succeeds in placing n of their marks in a horizontal, vertical, or diagonal row wins the game.
Example:
Given n = 3, assume that player 1 is "X" and player 2 is "O" in the board. TicTacToe toe = new TicTacToe(3); toe.move(0, 0, 1); -> Returns 0 (no one wins) |X| | | | | | | // Player 1 makes a move at (0, 0). | | | | toe.move(0, 2, 2); -> Returns 0 (no one wins) |X| |O| | | | | // Player 2 makes a move at (0, 2). | | | | toe.move(2, 2, 1); -> Returns 0 (no one wins) |X| |O| | | | | // Player 1 makes a move at (2, 2). | | |X| toe.move(1, 1, 2); -> Returns 0 (no one wins) |X| |O| | |O| | // Player 2 makes a move at (1, 1). | | |X| toe.move(2, 0, 1); -> Returns 0 (no one wins) |X| |O| | |O| | // Player 1 makes a move at (2, 0). |X| |X| toe.move(1, 0, 2); -> Returns 0 (no one wins) |X| |O| |O|O| | // Player 2 makes a move at (1, 0). |X| |X| toe.move(2, 1, 1); -> Returns 1 (player 1 wins) |X| |O| |O|O| | // Player 1 makes a move at (2, 1). |X|X|X|
Follow up:
Could you do better than O(n2) per
Could you do better than O(n2) per
move()
operation?
Thought process:
Use a counter for each row, column, and diagonal. If player one makes a move, increment counter. If player two makes a move, decrement counter. When any counter reaches n or -n, there is a winner.
Solution:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 | class TicTacToe { private int[] rows; private int[] cols; private int diagonal1; private int diagonal2; /** Initialize your data structure here. */ public TicTacToe(int n) { rows = new int[n]; cols = new int[n]; } /** Player {player} makes a move at ({row}, {col}). @param row The row of the board. @param col The column of the board. @param player The player, can be either 1 or 2. @return The current winning condition, can be either: 0: No one wins. 1: Player 1 wins. 2: Player 2 wins. */ public int move(int row, int col, int player) { int n = rows.length; int move = player == 1 ? 1 : -1; rows[row] += move; cols[col] += move; if (row == col) { diagonal1 += move; } if (row + col == n - 1) { diagonal2 += move; } if (Math.abs(rows[row]) == n || Math.abs(cols[col]) == n || Math.abs(diagonal1) == n || Math.abs(diagonal2) == n) { return player; } return 0; } } /** * Your TicTacToe object will be instantiated and called as such: * TicTacToe obj = new TicTacToe(n); * int param_1 = obj.move(row,col,player); */ |
Time complexity:
- Constructor: O(n).
- move(): O(1).
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