设T 是一棵带权树，树的每一条边带一个正权。又设S 是T 的顶点集,T/S 是从树T 中

将S中顶点删去后得到的森林。如果T/S中所有树的从根到叶的路长都不超过d ，则称T/S

是一个d 森林。

(1)设计一个算法求T的最小顶点集S，使T/S是d 森林。(提示：从叶向根移动)

(2)分析算法的正确性和计算复杂性。

(3)设T中有n 个顶点，则算法的计算时间复杂性应为O(n)。-based T is a right to bring a tree for every one of the sideband is the right one. S is also based Vertex Set T, T / S from the tree T Lieutenant General S vertex deletion the forest. If the T / S all trees from the roots to leaves of a long road, do not exceed d, said the T / S is a d forest. (1) design a T algorithm for the minimum vertex set S, T / S is d forest. (Tip : from roots to leaves mobile) (2) analysis algorithm correctness and computational complexity. (3) The T with n vertices, the algorithm complexity of computing time for the O (n).