Anticlockwise rotation of matrix

[linuxx]

Hello Guys,

If I rotate 2D array anticlockwise,h ow would I map original variables into new matrix?

Consider the example:
original matrix =

1 2 3
4 5 6
7 8 9

Final matrix =

3 6 9
2 5 8
1 4 7

Now If I want to access the 6 from original matrix.I'd use..
i = 1 and j =2..i.e. OriginalArr[i][j] will give me 6.

My question is, how could I access same number(here 6) from final matrix using previous i and j ?

One solution could be FinalnalArr[ i -1 ] [ j -1 ]
but this is not generalized.

I want general solution that work for any i,j as well as for any 2D matrix(any dimensions).

[JosAH]

Just look at your matrixes; let their dimension be NxN. Row i in the transformed
matrix is column N-1-i in the original matrix. Column j in the transformed matrix
is row j in the original matrix, so A[j][N-i-1] gives you the transformed matrix.

kind regards,

Jos

[linuxx]

Just look at your matrixes; let their dimension be NxN. Row i in the transformed
matrix is column N-1-i in the original matrix. Column j in the transformed matrix
is row j in the original matrix, so A[j][N-i-1] gives you the transformed matrix.

kind regards,

Jos

Hey Jos...
Don't forget, 2D array can have dimensions as MxN.
Your solution works for NxN.

[JosAH]

Hey Jos...
Don't forget, 2D array can have dimensions as MxN.
Your solution works for NxN.

It also works for an MxN matrix; check it out.

kind regards,

Jos

[linuxx]

It also works for an MxN matrix; check it out.

kind regards,

Jos

You've given me the formula...
A[j][N-i-1]
I was just wondering about N..should it be number of Rows or number of Columns
Any way...It's working...

Will you please explain me..how you figured out this formula?

[JosAH]

You've given me the formula...
A[j][N-i-1]
I was just wondering about N..should it be number of Rows or number of Columns
Any way...It's working...

Will you please explain me..how you figured out this formula?

I used a rotation matrix and rotated the indexes (col, row) which gives (-row, col),
then I fiddled a bit to get those index values back in the range [0, N)

kind regards,

Jos