Implementation of BFS for tic-tac-toe problem using Java.

 2. Implementation of BFS for tic-tac-toe problem using  Java.

Rules of the Playing Game:

• The game is to be played between two people (in this program between HUMAN and COMPUTER).
• One of the player chooses ‘O’ and the other ‘X’ to mark their respective cells.

• The game starts with one of the players and the game ends when one of the players has one whole row/ column/ diagonal filled with his/her respective character (‘O’ or ‘X’).
• If no one wins, then the game is said to be draw
  

In our program the moves taken by the computer and the human are chosen randomly. We use rand() function for this.

Winning Strategy – An Interesting Fact

If both the players play optimally then it is destined that you will never lose (“although the match can still be drawn”). It doesn’t matter whether you play first or second.In another ways – “ Two expert players will always draw ”.

Isn’t this interesting ?

Source Code

import java.util.*; public class GFG { static String[] board; static String turn; static String checkWinner() { for (int a = 0; a < 8; a++) { String line = null; switch (a) { case 0: line = board[0] + board[1] + board[2]; break; case 1: line = board[3] + board[4] + board[5]; break; case 2: line = board[6] + board[7] + board[8]; break; case 3: line = board[0] + board[3] + board[6]; break; case 4: line = board[1] + board[4] + board[7]; break; case 5: line = board[2] + board[5] + board[8]; break; case 6: line = board[0] + board[4] + board[8]; break; case 7: line = board[2] + board[4] + board[6]; break; } if (line.equals("XXX")) { return "X"; } else if (line.equals("OOO")) { return "O"; } } for (int a = 0; a < 9; a++) { if (Arrays.asList(board).contains(String.valueOf(a + 1))) { break; } else if (a == 8) { return "draw"; } } System.out.println(turn + "'s turn; enter a slot number to place " + turn + " in:"); return null; } static void printBoard() { System.out.println("|---|---|---|"); System.out.println("| " + board[0] + " | "+ board[1] + " | " + board[2]+ " |"); System.out.println("|-----------|"); System.out.println("| " + board[3] + " | "+ board[4] + " | " + board[5]+ " |"); System.out.println("|-----------|"); System.out.println("| " + board[6] + " | "+ board[7] + " | " + board[8]+ " |"); System.out.println("|---|---|---|"); } public static void main(String[] args) { Scanner in = new Scanner(System.in); board = new String[9]; turn = "X"; String winner = null; for (int a = 0; a < 9; a++) { board[a] = String.valueOf(a + 1); } System.out.println("Welcome to 3x3 Tic Tac Toe."); printBoard(); System.out.println("X will play first. Enter a slot number to place X in:"); while (winner == null) { int numInput; try { numInput = in.nextInt(); if (!(numInput > 0 && numInput <= 9)) { System.out.println("Invalid input; re-enter slot number:"); continue; } } catch (InputMismatchException e) { System.out.println("Invalid input; re-enter slot number:"); continue; } if (board[numInput - 1].equals(String.valueOf(numInput))) { board[numInput - 1] = turn; if (turn.equals("X")) { turn = "O"; } else { turn = "X"; } printBoard(); winner = checkWinner(); } else { System.out.println("Slot already taken; re-enter slot number:"); } } if (winner.equalsIgnoreCase("draw")) { System.out.println("It's a draw! Thanks for playing."); } else { System.out.println("Congratulations! " + winner+ "'s have won! Thanks for playing."); } } } code-box

Output