2026-10-17 16:48
Mathlib/Combinatorics/SimpleGraph/Acyclic.lean
feat(Combinatorics/SimpleGraph/Acyclic): a graph is a tree iff it's acyclic and has exactly `n - 1` edges (#34910)
Added SimpleGraph.isTree_iff_isAcyclic_and_ncard_edgeSet_add_one_eq_card