# Get the root node of a node
	# Use *path compression* to flatten the structure
	# ENSURE: `result.parent == result`
	private fun nfind(ne: DisjointSetNode): DisjointSetNode
	do
		var nf = ne.parent
		if nf == ne then return ne
		var ng = nfind(nf)
		ne.parent = ng
		return ng
	end