2D array rotation

Question

I have a 2D array that I would like to flip clockwise (no, this is not a homework assignment!). I have the following output as my code tries to flip the array by creating a new temporary one.

// Original array
I/System.out: 10 11 12 13 14 
I/System.out: 15 16 17 18 19 

// Temp array
I/System.out: 10 15 
I/System.out: 11 16 
I/System.out: 12 17 
I/System.out: 13 18 
I/System.out: 14 19

What I want is for the second array (15 - 19) to be in the first column. I just do not understand what I am doing wrong.

The code is as follows:

Object[][][] containerTemp = new Object[zDim][yDim][xDim];
for (int z = 0; z < zDim; z++) {
   for (int y = yDim - 1; y >= 0; y--) {
      for (int x = 0; x < xDim; x++) {
         containerTemp[z][y][x] = container[z][x][y];
      }
   }
}

The final result of the Temp array will be correct for the purpose of the project, but I have other code that will do this part, I just want these nested for loops to "flip" the array without moving the values.

You seem to be using "flip" and "rotate" interchangeably, but they aren't the same thing. — azurefrog
– azurefrog, Commented Jan 3, 2018 at 20:27
Debuggers are quite helpful in determining why code is working a certain way. Pen and paper would probably be just as useful in this case. — Jonny Henly
– Jonny Henly, Commented Jan 3, 2018 at 20:28
@azurefrog : Yes, sorry about that! I ment flip. You could think about it like a bookcase that is faced down. I would like to make it stand without the items in it changing. — goldenmaza
– goldenmaza, Commented Jan 3, 2018 at 20:59
@ Jonny Henly : Sometimes, yes. It did not help me this time. @AndyTurner : Yes, I didn't know what thing existed until today. But that is what I am trying to do as my earlier solution actually moved values around in the matrix. — goldenmaza
– goldenmaza, Commented Jan 3, 2018 at 21:06

David Pérez Cabrera · Accepted Answer · 2018-01-03 20:38:57Z

1

Try with:

Object[][][] containerTemp = new Object[zDim][yDim][xDim];
for (int z = 0; z < zDim; z++) {
   for (int y = yDim - 1; y >= 0; y--) {
      for (int x = 0; x < xDim; x++) {
         containerTemp[z][y][xDim - (x + 1)] = container[z][x][y]; // change x target.
      }
   }

}

answered Jan 3, 2018 at 20:38

David Pérez Cabrera

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2 Comments

goldenmaza Over a year ago

It worked! Thank you! Could you explain the difference between what I wrote and what changes you made to make it work?! Thank you!

David Pérez Cabrera Over a year ago

@goldenmaza I added a step after traspose: It flips horizontally ('x' coordinate).

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