Possible cycle types of permutations #
- For
m : Multiset ℕ
,Equiv.Perm.exists_with_cycleType_iff m
proves that there are permutations with cycleTypem
if and only if its sum is at mostFintype.card α
and 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), g.cycleType = m) ↔ m.sum ≤ 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.