CareerCup

Naive Java implementation:

public class TicTacToe {
	private int fieldSize;
	private int[] rowCounter = new int[3];
	private int[] colCounter = new int[3];
	private int[] diagCounter = new int[2];
	private boolean[][] checkMark = new boolean[3][3];
	public TicTacToe(int fieldSize){
		if (fieldSize < 3){
			this.fieldSize = 3;public class TicTacToe {
	private int fieldSize;
	private int[] rowCounter = new int[3];
	private int[] colCounter = new int[3];
	private int[] diagCounter = new int[2];
	private boolean[][] checkMark = new boolean[3][3];
	public TicTacToe(int fieldSize){
		if (fieldSize < 3){
			this.fieldSize = 3;
		} else {
			this.fieldSize = fieldSize;
		}
		this.rowCounter = new int[this.fieldSize];
		this.colCounter = new int[this.fieldSize];
		this.checkMark = new boolean[this.fieldSize][this.fieldSize]; 
		for (int i=0; i<this.fieldSize; ++i){
			this.rowCounter[i] = 0;
			this.colCounter[i] = 0;
		}
	}

	private TicTacToe(){}

	/** place mark function, (x, y) pins the position and 'player' should be either -1 or 1
	 * 
	 * @param x
	 * @param y
	 * @param player
	 * @return 1: 1p wins, 2: 2p wins, -1: x | y out of bounds; 0: just another day at the office
	 */
	public int placeMark(int x, int y, int player){
		if((x>fieldSize && x<0) || (y>fieldSize && y<0)){
			return -1;
		}
		if(!(player == -1 || player == 1)){
			return -1;
		}
		if(this.checkMark[x][y]){
			return -1;
		} else {
			this.checkMark[x][y] = true;
		}
		
		this.rowCounter[x] += player;
		if(isWin(this.rowCounter, x)!=0){return isWin(this.rowCounter, x);}
		this.colCounter[y] += player;
		if(isWin(this.colCounter, y)!=0){return isWin(this.colCounter, y);}
		
		if(x==y){
			this.diagCounter[0] += player;
			if(isWin(this.diagCounter, 0)!=0){return isWin(this.diagCounter, 0);}
			this.diagCounter[1] += player;
			if(isWin(this.diagCounter, 1)!=0){return isWin(this.diagCounter, 1);}
		} else {
			if(x+y==this.fieldSize+1){
				this.diagCounter[1] += player;
				if(isWin(this.diagCounter, 1)!=0){return isWin(this.diagCounter, 1);}
			}
		}
		return 0;
	}
	
	private int isWin(int[] counter, int index){
		if (Math.abs(counter[index])==this.fieldSize){
			if (counter[index] < 0) {return 1;} else {return 2;} 
		}
		return 0;
	}
}
		} else {
			this.fieldSize = fieldSize;
		}
		this.rowCounter = new int[this.fieldSize];
		this.colCounter = new int[this.fieldSize];
		this.checkMark = new boolean[this.fieldSize][this.fieldSize]; 
		for (int i=0; i<this.fieldSize; ++i){
			this.rowCounter[i] = 0;
			this.colCounter[i] = 0;
		}
	}

	private TicTacToe(){}

	/** place mark function, (x, y) pins the position and 'player' should be either -1 or 1
	 * 
	 * @param x
	 * @param y
	 * @param player
	 * @return 1: 1p wins, 2: 2p wins, -1: x | y out of bounds; 0: just another day at the office
	 */
	public int placeMark(int x, int y, int player){
		if((x>fieldSize && x<0) || (y>fieldSize && y<0)){
			return -1;
		}
		if(!(player == -1 || player == 1)){
			return -1;
		}
		if(this.checkMark[x][y]){
			return -1;
		} else {
			this.checkMark[x][y] = true;
		}
		
		this.rowCounter[x] += player;
		if(isWin(this.rowCounter, x)!=0){return isWin(this.rowCounter, x);}
		this.colCounter[y] += player;
		if(isWin(this.colCounter, y)!=0){return isWin(this.colCounter, y);}
		
		if(x==y){
			this.diagCounter[0] += player;
			if(isWin(this.diagCounter, 0)!=0){return isWin(this.diagCounter, 0);}
			this.diagCounter[1] += player;
			if(isWin(this.diagCounter, 1)!=0){return isWin(this.diagCounter, 1);}
		} else {
			if(x+y==this.fieldSize+1){
				this.diagCounter[1] += player;
				if(isWin(this.diagCounter, 1)!=0){return isWin(this.diagCounter, 1);}
			}
		}
		return 0;
	}
	
	private int isWin(int[] counter, int index){
		if (Math.abs(counter[index])==this.fieldSize){
			if (counter[index] < 0) {return 1;} else {return 2;} 
		}
		return 0;
	}
}

The following functions -

class TicTacToe
{
......
};

constructor- > should Initialize the board , register 2 players , assign X & O to them .
Start() --> Starts a Timer for Player whose move it is to make his move .
//should contain the logic for time Out .

IsGameOver() --> if anybody has won the game / Draw / Aborted .
IsADraw() , IsWon() etc .

Stop() -> should clean up all the resources .

Class Player
{
...
};

should contain functions like myTurn , hasWon etc .

Implementation -

The Board should be represented using bitboard i.e an array of 9 bits . This results in O(1) checking of various details .