Decomposition as a product of disjoint cycles : permu2cycles

### 2.10.2 Decomposition as a product of disjoint cycles :
`permu2cycles`

`permu2cycles` takes as argument a permutation.
`permu2cycles` returns its decomposition as a product of disjoint cycles.
Input :

`permu2cycles([1,3,4,5,2,0])`

Output :

`[[0,1,3,5],[2,4]]`

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).
Input :

`permu2cycles([0,1,2,4,3,5])`

Output :

`[[5],[3,4]]`

Input :

`permu2cycles([0,1,2,3,5,4])`

Output :

`[[4,5]]`