//let's make a 2d int array that stores the following:
  1 2 3  
  4 5 6

  int[][] a = new int[2][3]    
   for (int j=0; j<=1; j++){
     for (int i =0; i<=2; i++){
       a[j][i] = i+1 + j*3;
     }
    } 
//change number j<1 and i<2 in the above for-loops to M and N to get a M*N array with number 1,2,3,...,M*N layout in rows.

//printing the 2d array on screen:
for (int j=0; j< a.length; j++){
     for (int i =0; i< a[j].length; i++){  //each row per line, with space between elements
       System.out.print(a[j][i] + " ");
     }
     System.out.println();
}
     
  
//recall the array a above:
//  1 2 3  
//  4 5 6
// we can change the first row as follows:

a[0] = {1,2,3, 10, 12, 17, 20}

//now we get:
    1 2 3 10 12 17 20
    4 5 6 
//so it's not a sqare array anymore
a[0][4]
a[1][4] //there is not 5th element on the second row!
a.length
a[0].length  //7 elements in the first row
a[1].length  //3 element in the second row:    


//ok for the next few lectures, we will write a Tic-Tac-Toe game to practice with everything we learned so far.
//we will have the game both in the text mode and in GUI form!
//first we need to develop the "game engine"
//we need a square grid to put 'X' and 'O' on it.
//char[][] a: a is an array of array of int


TicTacToe t = new TicTacToe();

/*Let's make the state of the board as follows
X O
 X
 
*/
t.setMark('X', 0, 0)
t.setMark('O', 0, 2)  
t.setMark('X',1, 1)

/*let's write a toString method that makes a nice String out of the board:
X| |O
- - - 
 |X| 
- - - 
 | | 
 
in string form it actually:   "X| |O\n- - -\n |X|\n - - -\n | | " 
*/
t.toString()
t.toString()
t.toString()
TicTacToe t = new TicTacToe();
t.toString()

t.setMark('X', 0,0)
System.out.println(t.tiString)  //or System.out.println(t)
t.setMark('O', 0, 2)  
System.out.println(t)
t.setMark('X',1, 1)
System.out.println(t)