We study the recently introduced Connected Feedback Vertex Set (CFVS) problem
from the view-point of parameterized algorithms. CFVS is the connected variant
of the classical Feedback Vertex Set problem and is defined as follows: given a
graph G=(V,E) and an integer k, decide whether there exists a subset F of V, of
size at most k, such that G[V F] is a forest and G[F] is connected. We show
that Connected Feedback Vertex Set can be solved in time $O(2^{O(k)}n^{O(1)})$
on general graphs and in time $O(2^{O(\sqrt{k}\log k)}n^{O(1)})$ on graphs
excluding a fixed graph H as a minor. Our result on general undirected graphs
uses as subroutine, a parameterized algorithm for Group Steiner Tree, a well
studied variant of Steiner Tree. We find the algorithm for Group Steiner Tree
of independent interest and believe that it will be useful for obtaining
parameterized algorithms for other connectivity problems.

研究了连接反馈顶点集（Connected Feedback Vertex Set）问题的参数化算法，论述了该问题在图论领域的应用，证明了在普通图上复杂度为 O (2^O (k) n^O (1))，在不包含固定图 H 的图上复杂度为 O (2^O (√k logk) n^O (1))，此外将 Group Steiner Tree 问题用作子程序，并认为其独立于其他算法，具有重要意义。