An approximation algorithm for the maximum leaf spanning arborescence problem
Matthew Drescher, Adrian R. Vetta · ACM Transactions on Algorithms · 2010
We present an O (√opt)-approximation algorithm for the maximum leaf spanning arborescence problem, where opt is the number of leaves in an optimal spanning arborescence. The result is based upon an O (1)-approximation algorithm for a special class of directed graphs called willows. Incorporating the method for willow graphs as a subroutine in a local improvement algorithm gives the bound for general directed graphs.