240613 틱택토

static char[][] board;

public static void main(String[] args) throws Exception {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	StringBuilder resultBuilder = new StringBuilder();
	
	while (true) {
		String input = br.readLine();
		if (input.equals("end")) {
			break;
		}
		
		board = new char[3][3];
		int xCount = 0;
		int oCount = 0;
		
		for (int i = 0; i < 9; i++) {
			char current = input.charAt(i);
			board[i / 3][i % 3] = current;
			if (current == 'X') {
				xCount++;
			} else if (current == 'O') {
				oCount++;
			}
		}

		boolean valid = (xCount == oCount + 1 && ((xCount + oCount == 9 && !isBingo('O')) || (isBingo('X') && !isBingo('O'))))
						|| (xCount == oCount && isBingo('O') && !isBingo('X'));

		resultBuilder.append(valid ? "valid\n" : "invalid\n");
	}
	
	System.out.print(resultBuilder);
	br.close();
}

public static boolean isBingo(char player) {
	for (int i = 0; i < 3; i++) {
		if (board[i][0] == player && board[i][1] == player && board[i][2] == player) {
			return true;
		}
		if (board[0][i] == player && board[1][i] == player && board[2][i] == player) {
			return true;
		}
	}
	
	if (board[0][0] == player && board[1][1] == player && board[2][2] == player) {
		return true;
	}

	if (board[0][2] == player && board[1][1] == player && board[2][0] == player) {
		return true;
	}

	return false;
}

출처:https://www.acmicpc.net/problem/7682