Array swap - 2d array

Question

I'm working on swapping indices in a two-dimensional array. I seem to be on the right track, but it's not swapping the array in the way I want.

The first row's index j needs to be swapped with row 2's index j:

for (int j = 0; j < array.length ; j++){  
     int temp = array[row1][j]
     array[row1][j]=array[j][row1]
     array[j][row1] = temp ;
}

Any ideas on how to best approach this would be appreciated.

Please tell us what is "the way you want. Are you trying to transpose a square matrix? — Sergey Kalinichenko
– Sergey Kalinichenko, Commented Nov 8, 2012 at 0:22
do you want to get from [[0,1,2,3,4],[5,6,7,8,9]] to [[5,6,7,8,9],[0,1,2,3,4]]? — mreithub
– mreithub, Commented Nov 8, 2012 at 1:23
Yes. However, do keep in mind I have 4 rows. They aren't swappable in a specific order. I can swap row 1 with row 3 if I want, or row 2 with row -1, etc. — TimelordViktorious
– TimelordViktorious, Commented Nov 8, 2012 at 1:30

mreithub · Accepted Answer · 2012-11-08 01:55:56Z

4

As the two-dimensional array in java is actually a array of references to other arrays, you can simply swap the references as shown below:

public static void swapRows(int array[][], int rowA, int rowB) {
   int tmpRow[] = array[rowA];
   array[rowA] = array[rowB];
   array[rowB] = tmpRow;
}

/edit: edited the answer as I previously misinterpreted it**

edited Nov 8, 2012 at 1:55

answered Nov 8, 2012 at 0:30

mreithub

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3 Comments

mreithub Over a year ago

hmmm, I guess one could even start at int col=row+1 as e.g. array[10][10] doesn't need swapping with its opposite

TimelordViktorious Over a year ago

Nope. I'm still not getting this right. I have to loop through indices j, and swap those indices from the first row to the 2nd row.

mreithub Over a year ago

@MH1993 Edited the answer. Is that what you want?

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