LeetCode – Tic-Tac-Toe (Java)

Design a Tic-tac-toe game that is played between two players on a n x n grid.

Java Solution 1 - Naive

We can simply check the row, column and the diagonals and see if there is a winner.

public class TicTacToe {
 
    int[][] matrix;
 
    /** Initialize your data structure here. */
    public TicTacToe(int n) {
        matrix = new int[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) {
        matrix[row][col]=player;
 
        //check row
        boolean win=true;
        for(int i=0; i<matrix.length; i++){
            if(matrix[row][i]!=player){
                win=false;
                break;
            }
        }
 
        if(win) return player;
 
        //check column
        win=true;
        for(int i=0; i<matrix.length; i++){
            if(matrix[i][col]!=player){
                win=false;
                break;
            }
        }
 
        if(win) return player;
 
        //check back diagonal
        win=true;
        for(int i=0; i<matrix.length; i++){
            if(matrix[i][i]!=player){
                win=false;
                break;
            }
        }
 
        if(win) return player;
 
        //check forward diagonal
        win=true;
        for(int i=0; i<matrix.length; i++){
            if(matrix[i][matrix.length-i-1]!=player){
                win=false;
                break;
            }
        }
 
        if(win) return player;
 
        return 0;
    }
}

Java Solution 2

public class TicTacToe {
    int[] rows;
    int[] cols;
    int dc1;
    int dc2;
    int n;
    /** Initialize your data structure here. */
    public TicTacToe(int n) {
        this.n=n;
        this.rows=new int[n];
        this.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 val = (player==1?1:-1);
 
        rows[row]+=val;
        cols[col]+=val;
 
        if(row==col){
            dc1+=val;
        }
        if(col==n-row-1){
            dc2+=val;
        }
 
        if(Math.abs(rows[row])==n 
        || Math.abs(cols[col])==n 
        || Math.abs(dc1)==n 
        || Math.abs(dc2)==n){
            return player;
        }
 
        return 0;
    }
}
Category >> Algorithms  
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