A 2-Approximation Algorithm for Finding a Spanning Tree with Maximum Number of Leaves

We study the problem of finding a spanning tree with maximum number of leaves. We present a simple 2-approximation algorithm for the problem, improving on the approximation ratio of 3 achieved by the best previous algorithms. We also study the variant in which a given set of vertices must be leaves of the spanning tree, and we present a 5/2-approximation algorithm for this version of the problem.