n

n-1

n+1

2n-1

maximum of n,d

n+d

nd

nd/2

A-2 , B-4 , C-1 , D-3

A-3 , B-4 , C-1 , D-2

A-3 , B-4 , C-2 , D-1

A-4 , B-1 , C-2 , D-3

n x (i -1) + j

m x (j -1) + i

m x (n-j) + j

n x (m-i) + j

higher dimension

many non-zero entries

many zero entries

higher dimension and many non-zero entries