Java Matrix using Arrays

Question

I'm struggling to find an answer to the problem below. User inputs rows and columns. Example below is given for 4 x 4 matrix.

1 8 9 16

2 7 10 15

3 6 11 14

4 5 12 13

I cannot find how to relate the numbers when printing the array. The only obvious relation is how it goes downwards and upwards. From my perspective looks really hard. I'm just a beginner.

Not quite sure if there is any point to post the code, but it's just the basic lines:

public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.println("Please enter your array rows: ");
    int rows = scanner.nextInt();

    System.out.println("Please enter your array columns: ");
    int columns = scanner.nextInt();

    int[][] array = new int[rows][columns];

    int counter = 0;
    for (int j = 0; j < columns; j++){
        for (int i = 0; i < rows; i++) {
            counter++;
            array[i][j]=...(stuck at the beginning);
        }

Probably I'd need to use several loops , not only the above-mentioned or probably it is totally wrong ... Thank you in advance!

you should store it row-wisely, array[0][0] = 1; array[1,3] = 15; array[2][1]=3 — apramc
– apramc, Commented Aug 30, 2015 at 17:47
Yes, sorry. I noticed I reversed them. Should be rows then columns. But still need help for it. — user3633880
– user3633880, Commented Aug 30, 2015 at 17:53
Must be a class going on. Here are now 7 questions created in the last hour exactly like this one. — Andreas
– Andreas, Commented Aug 30, 2015 at 17:54
from where the number 1 8 9 16 2 7 10 15 3 6 11 14 4 5 12 13 come from? — Nabin Bhandari
– Nabin Bhandari, Commented Aug 30, 2015 at 17:57

Sumeet · Accepted Answer · 2015-08-30 18:01:29Z

1

I think this should do it.

    int counter = 0;
    boolean top_to_bottom=true;
    for (int j = 0; j < columns; j++){
        for (int i = 0; i < rows; i++) {
            counter++;
            if(top_to_bottom)
             array[i][j]=counter;
            else
             array[rows-1-i][j]=counter;
        }
        if(top_to_bottom)
         top_to_bottom=false;
        else top_to_bottom=true;
    }

answered Aug 30, 2015 at 18:01

Sumeet

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1 Comment

user3633880 Over a year ago

Great ! Thank you! So actually in the 'for' statement it has to be columns first, then rows ?

Manish · Accepted Answer · 2015-08-30 18:15:04Z

It serves the purpose

import java.util.*;

public class Seq

{

public static void main(String[] args)

{

Scanner scanner = new Scanner(System.in);

System.out.println("Please enter your array rows: ");

int rows = scanner.nextInt();

System.out.println("Please enter your array columns: ");

int columns = scanner.nextInt();

 int[][] array = new int[rows][columns];

  int counter = 0;

for (int j = 0; j < columns; j++){

if(j%2==0) {

 for (int i = 0; i < rows; i++)
     {
        counter=counter+1;
            array[i][j]=counter;

        }
 } 
else

 {
      for (int i = rows-1; i >=0; i--) 

          {
                counter=counter+1;

                array[i][j]=counter;

            }
     }

  }

  for(int i=0;i<rows;i++)

    {

        for(int j=0;j<columns;j++)
      {

        System.out.print(array[i][j]+" ");

        }
        System.out.println();
         }
   }

}

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