Initialize 2D array using nested for loops and finding a pattern

Question

I'm trying to figure out how nested for loops for initializing variables work. I looked at another question on here that initialized values in a 2D array from 1 to 15 which seemed reasonable using the code:

 for (int i = 0; i < row.length; i++) {
        for (int j = 0; j < row[0].length; j++) {
            row[i][j] = (i * row[0].length) + j;
        }
    }

I'm trying to extend that idea so that another array has the pattern as follows:

 {0, 9,18,27,36,45,54,63,72} //row0...row8
 { 1,10,19,28,37,46,55,64,73}

It obvious that once a row completes a number is incremented by 1 and you keep adding 9 until you get to the end of the row. How is this represented in code? Solution to this problem would be great but a more general approach would be appreciated more if possible. My guess is that the headings for the for loop statements don't change but rather its the assignment equation that does.

Paul Draper · Accepted Answer · 2013-11-13 02:20:52Z

1

for (int i = 0; i < row.length; i++) {
    for (int j = 0; j < row[j].length; j++) {
        row[i][j] = i + j * 9;
    }
}

edited Nov 13, 2013 at 2:20

answered Nov 13, 2013 at 2:15

Paul Draper

84.2k53 gold badges216 silver badges303 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

nitiger Over a year ago

I'm curious. Can I just flip the j and i in row[i][j] = ... to make it row[j][i]=...? I get the answer I want but would this make any difference in the long run?

Paul Draper Over a year ago

It depends what you are flipping... if you mean j + i * 9, you can certainly do that.

nitiger Over a year ago

Yeah, I really should think more before posting on here sigh... Thank you for your response.

Shelvacu · Accepted Answer · 2013-11-13 02:14:13Z

1

Would this work?

for(int i=0; i < 9; i++){
  for(int j=0; j < 9; j++){
    row[i][j] = j+i;
  }
}

answered Nov 13, 2013 at 2:14

Shelvacu

4,42028 silver badges47 bronze badges

1 Comment

Shelvacu Over a year ago

it doesn't, I apologize.

Mengjun · Accepted Answer · 2013-11-13 02:21:33Z

Have a try with the following code:

    int[][] row = new int[9][9];
    for (int i = 0; i < row.length; i++) {
        row[i][0] = i;
        for (int j = 1; j < row[i].length; j++) {
            row[i][j] = row[i][j - 1] + 9;
        }
    }

    /*
     * Print 2d-array
     */

    for (int i = 0; i < row.length; i++) {
        for (int j = 0; j < row[i].length; j++) {
            System.out.printf("%2d ", row[i][j]);
        }
        System.out.println();
    }

Output in Console:

 0  9 18 27 36 45 54 63 72 
 1 10 19 28 37 46 55 64 73 
 2 11 20 29 38 47 56 65 74 
 3 12 21 30 39 48 57 66 75 
 4 13 22 31 40 49 58 67 76 
 5 14 23 32 41 50 59 68 77 
 6 15 24 33 42 51 60 69 78 
 7 16 25 34 43 52 61 70 79 
 8 17 26 35 44 53 62 71 80

Collectives™ on Stack Overflow

Initialize 2D array using nested for loops and finding a pattern

3 Answers 3

3 Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

3 Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related