CODEWITHSUNDEEP
javaarraysmultidimensional-array
dalold
dalold

Reputation: 145

Java 2D array manipulation - shifting columns associated with rows

I have a 2D array which looks like this:

   0  1  2  3  4
0 [4, 5, 6, 7, 9]
1 [9, 2, 1, 6, 4]
2 [0, 0, 0, 0, 0]
3 [8, 7, 6, 4, 1]
4 [0, 0, 0, 0, 0]

I would like to change the order of the rows and then change the columns so they match up to the original order i.e. (1,1) would stay as 2. So when I swap the rows I get:

   0  1  2  3  4
2 [0, 0, 0, 0, 0]
4 [0, 0, 0, 0, 0]
0 [4, 5, 6, 7, 9]
1 [9, 2, 1, 6, 4] 
3 [8, 7, 6, 4, 1]

I am able to do this in code. But what I can't wrap my head around is how to change the columns according to the switch. So in the end I would like: 

   2  4  0  1  3
2 [0, 0, 0, 0, 0]
4 [0, 0, 0, 0, 0]
0 [6, 9, 4, 5, 7]
1 [1, 4, 9, 2, 6] 
3 [6, 1, 8, 7, 4]

Where the original row -> column indices mapping remains. Could anyone give me some tips on how to approach this problem?

Upvotes: 1

Views: 135

Answers (2)

William V
William V

Reputation: 78

Remember that a 2D array is just an array of arrays. What you are calling columns are not actually a part of the structure, rather just the same spot in each of the arrays. To switch a column, you need to switch the same spot in each of the arrays.

Upvotes: 0

JoshKopen
JoshKopen

Reputation: 960

Here is my suggestion for some pseudocode which should solve your problem:

  • First create a new array with the same dimensions without deleting the old one.
  • Next randomize the order of your rows.
  • Next randomize your columns.
  • Then use your original table and the new places for your new row and column order to completely repopulate the table according to origninal coordinates.

By never deleting the old table, you can very easily reference back to it to repopulate your new table.

Upvotes: 1

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