12.2.3  Decomposing a permuation into a product of disjoint cycles

Any permutation can be decomposed as a sequence of cycles which have no elements in common. For example, the permutation [1,3,4,0,2] can be written as a combination of the cycles [0,1,3] and [2,4].

The permu2cycles command decomposes a permutation into a combination of cycles.

• permu2cycles takes p, a permutation.
• permu2cycles(p) returns the decomposition of p as a product of disjoint cycles. A cycle is represented by a list, a cyclic decomposition is represented by a list of lists.

Examples

In the answer the cycles of size 1 are omitted, except if n−1 is a fixed point of the permutation (this is required to find the value of n from the cycle decomposition).