How to iterate through a 2D Array with a string of permutations?

Question

I have a 2D array which is a square matrix 4x4.

First I generated the permutation of '1234' S = "1234124313241423........."(in fact it should be '0123', Let's ignore that for now.) if it's 5x5 it would be '12345'

I would like to iterate through a 2D array and sum every 4 elements with the following fashion:

The row-index follow the fixed pattern 1234,1234,1234.
The column-index is pulled from the permuted string.

input 2D Array which is a 4x4 matrix:

{9,2,7,8},
{6,4,3,7},
{5,8,1,8},
{7,6,9,4}

the 2D array can be represented as a[i][j], i for rows and j for columns, columns are pulled from S = "1234124313241423" chop every 4 digits from the string.

                                  index          index
Read from left to right

a11+a22+a33+a44    => 9+4+1+4=18     rows: 1 2 3 4  columns: 1 2 3 4

a11+a22+a34+a43    => 9+4+8+9=30     rows: 1 2 3 4  columns: 1 2 4 3

a11+a23+a32+a44    => 9+3+8+4=24     rows: 1 2 3 4  columns: 1 3 2 4

a11+a24+a32+a43    ...........
   .
   .
   .

output:18,30,24,....

It seems like a standard nested loop won't do the job.

Is your question how to create a 2-D array here, or how to iterate through it? — Robo Mop
– Robo Mop, Commented Mar 24, 2018 at 4:25
@CoffeehouseCoder Hi sorry for the confusion. I would like to iterate through a 2D array. — gqli
– gqli, Commented Mar 24, 2018 at 4:26

Art · Accepted Answer · 2018-04-02 07:51:24Z

1

You need to have an outer loop which will iterate no of rows times... Then for each of that iteration increment i and j both and get the value S[i][j] Outer loop can be like while(k< noOfRows).. i am leaving the program for you to practise...

edited Apr 2, 2018 at 7:51

answered Mar 24, 2018 at 5:43

Art

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Shubham Agarwal Bhewanewala · Accepted Answer · 2018-03-24 05:51:49Z

0

String s = "123412431324...";
while(s.length() != 0){
  int sum=0;
  for(int j=0, i=0; j<n; j++, i++){
    sum += arr[i][Integer.parseInt(s.charAt(j))-1];
  }
  System.out.println(sum);
  s = s.substring(n);
}

Your can perform like this. You need a outer loop which can slice up your string by dimension of your array and another loop for iterating through your array so that you can sum up the elements.[Check the for loop carefully]

edited Mar 24, 2018 at 5:51

answered Mar 24, 2018 at 5:43

Shubham Agarwal Bhewanewala

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