Data Structures, Algorithms, & Applications in C++
Chapter 7, Exercise 35

(a)

A sample antidiagonal matrix is given below:

0 0 0 1
0 0 3 0
0 0 0 0
6 0 0 0


(b)

In an antidiagonal matrix there can be at most one nonzero entry in each row; for row i, this nonzero entry is in column n+1-i. Therefore, an n x n antidiagonal matrix can have at most n nonzero entries. A test program and output appear in the files AntidiagonalMatrix.*.

(c)

We can put the antidiagonal element M(i, n+1-j) in position i-1 of a one-dimensional array.