Tic Tac Toe - Amazon Top Interview Questions


Problem Statement :


Implement the tic-tac-toe game with the following methods:

TicTacToe(int n) which instantiates an n x n game board. A player wins a game if their pieces either form a horizontal, vertical, or diagonal line of length n.
int move(int r, int c, boolean me) which places the next move at row r and column c. me indicates whether it's my move (me = true) or it's your opponent's (me = false) move. If this move makes you win, return 1, if your opponent wins, return -1, and otherwise return 0.
Constraints

1 ≤ n ≤ 100,000

0 ≤ m ≤ 100,000 where m is the number of calls to move

Example 1

Input

methods = ["constructor", "move", "move", "move", "move", "move"]

arguments = [[3], [0, 0, True], [2, 0, False], [0, 1, True], [2, 1, False], [0, 2, True]]`

Output

[None, 0, 0, 0, 0, 1]

Explanation

t = TicTacToe(3)

t.move(0, 0, True) == 0 # I place piece (0, 0)

t.move(2, 0, False) == 0 # Opponent places piece (2, 0)

t.move(0, 1, True) == 0 # I place piece (0, 1)

t.move(2, 1, False) == 0 # Opponent places piece (2, 1)

t.move(0, 2, True) == 1 # I place piece (0, 2) to win


Solution :



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                        Solution in C++ :

class TicTacToe {
    int n;
    unordered_map<int, int> row[2], col[2], diag[2], cross[2];

    public:
    TicTacToe(int n) : n(n) {
    }

    int move(int r, int c, bool me) {
        int winner = 2 * me - 1;
        if (++row[me][r] == n) return winner;
        if (++col[me][c] == n) return winner;
        if (++diag[me][r + c] == n) return winner;
        if (++cross[me][r - c] == n) return winner;
        return 0;
    }
};
                    


                        Solution in Java :

import java.util.*;

class TicTacToe {
    int n;
    int[] rowSum;
    int[] colSum;
    int diag;
    int revDiag;

    public TicTacToe(int n) {
        this.n = n;
        rowSum = new int[n];
        colSum = new int[n];
        diag = 0;
        revDiag = 0;
    }

    public int move(int r, int c, boolean me) {
        // Step 1) Make a move
        int val = me ? 1 : -1;
        rowSum[r] += val;
        colSum[c] += val;

        if (r == c)
            diag += val;
        if (r == n - c - 1)
            revDiag += val;

        // Step 2) Check if game over
        boolean gameOver = Math.abs(rowSum[r]) == n || Math.abs(colSum[c]) == n
            || Math.abs(diag) == n || Math.abs(revDiag) == n;

        if (gameOver)
            return me ? 1 : -1;
        return 0;
    }
}
                    


                        Solution in Python : 
                            
class TicTacToe:
    def __init__(self, n):
        self.n = n
        self.row_sums = [0] * n
        self.col_sums = [0] * n
        self.diag = self.inv_diag = 0

    def move(self, r, c, me):
        val = 1 if me else -1

        # update values
        self.row_sums[r] += val
        self.col_sums[c] += val
        if r == c:
            self.diag += val
        if r == self.n - c - 1:
            self.inv_diag += val

        # check wins
        if self.n in list(map(abs, [self.row_sums[r], self.col_sums[c], self.diag, self.inv_diag])):
            return val
        return 0


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