Possible cycle types of permutations #
- For
m : Multiset ℕ,Equiv.Perm.exists_with_cycleType_iff mproves that there are permutations with cycleTypemif and only if its sum is at mostFintype.card αand its members are at least 2.
theorem
Equiv.Perm.exists_with_cycleType_iff
(α : Type u_1)
[DecidableEq α]
[Fintype α]
{m : Multiset ℕ}
:
(∃ (g : Equiv.Perm α), Equiv.Perm.cycleType g = m) ↔ Multiset.sum m ≤ Fintype.card α ∧ ∀ a ∈ m, 2 ≤ a
There are permutations with cycleType m if and only if
its sum is at most Fintype.card α and its members are at least 2.