Design Tic-Tac-Toe

题目
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.

答案

class TicTacToe {

    Map<String, int[]> map;
    int n;
    /** Initialize your data structure here. */
    public TicTacToe(int n) {
        map = new HashMap<>();
        this.n = 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) {
        // Placing a piece on board[row][col] affects 1 row, 1 col, and 0/1/2 diagonals
        String k1 = "r" + Integer.toString(row);
        String k2 = "c" + Integer.toString(col);
        String k3 = "", k4 = "";
        
        int[] r_cnt = map.get(k1);
        if(r_cnt == null) {
            r_cnt = new int[2];
            map.put(k1, r_cnt);
        }
        r_cnt[player - 1]++;
        
        int[] c_cnt = map.get(k2);
        if(c_cnt == null) {
            c_cnt = new int[2];
            map.put(k2, c_cnt);
        }
        c_cnt[player - 1]++;
        
        if(row == col) {
            k3 = "d1#";
            int[] d1_cnt = map.get(k3);
            if(d1_cnt == null) {
                d1_cnt = new int[2];
                map.put(k3, d1_cnt);
            }
            d1_cnt[player - 1]++;
        }
        
        if(row == this.n - col - 1) {
            k4 = "d2#";
            int[] d2_cnt = map.get(k4);
            if(d2_cnt == null) {
                d2_cnt = new int[2];
                map.put(k4, d2_cnt);
            }
            d2_cnt[player - 1]++;
        }
        
        // Check if end condition is met
        return check();
    }
    
    private int check() {
        for(Map.Entry<String, int[]> entry : map.entrySet()) {
            String k = entry.getKey();
            int[] cnt = entry.getValue();
            if(cnt[0] == this.n) return 1;
            if(cnt[1] == this.n) return 2;
        }
        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);
 */