Function inverse

Computes the inverse of a row.

From Knuth 1.3.3:

The inverse π^- of a permutation π is the rearrangement that undoes the effect of π; if i goes to j under π, then j goes to i under π^-. Thus the product ππ^- equals the identity permutation, and so does the product π^-π.

> inverse([5, 3, 1, 2, 4, 6])
[3, 4, 2, 5, 1, 6]
> multiply([5, 3, 1, 2, 4, 6], inverse([5, 3, 1, 2, 4, 6]))
[1, 2, 3, 4, 5, 6]
> multiply(inverse([5, 3, 1, 2, 4, 6]), [5, 3, 1, 2, 4, 6])
[1, 2, 3, 4, 5, 6]
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A new row is returned; the original is left unchanged.