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4582：DFS spanning tree

题目描述
Consider a Depth-First-Search(DFS) spanning tree T of a undirected connected graph G, we define a T-Simple Circle as a path v1, v2, ..., vk (v1 = vk) in G that contains at most one edge which not belongs to the DFS spanning tree T.
Given a graph G, we process DFS on G starting from vertex 1 and get a DFS spanning tree T, then you should choose some edges of G so that all T-Simple Circles contains at least one edge that you choose.
Please minimize the number of edges you choose.
输入解释
There are at most 100 test cases.
For each case, the first line contains two integers n and m denoting the number of vertices and edges. The vertexes are numbered from 1 to n.
The following m lines describe the graph. Each line contains two integers xi and yi, denoting an edge between vertex xi and yi(xi ≠ yi).
Note that the first n-1 edges of input construct a DFS spanning tree T which is generated by DFS from vertex 1.
Input ends with n = 0 and m = 0
(1 <= n <= 2000, 1 <= m <= 20000, 1 <= xi, yi <= n)
输出解释
For each case, output the number of minimal edges that you choose.
输入样例 
4 5
1 2
4 2
3 2
1 3
4 1
10 14
1 2
2 9
1 3
3 4
4 10
3 5
5 7
5 8
3 6
9 1
1 10
1 6
7 3
8 3
0 0
输出样例 
1
3
提示
ere is the graph G in the first test case: 

 
The solid lines denote the edge which belongs to the DFS spanning tree, and the dotted lines denote the others.
For first case, we can choose one edge (1, 2)
For second case, we can choose three edges (1, 2), (1, 3), (3, 5)
来自杭电HDUOJ的附加信息
Recommend
该题目是Virtual Judge题目，来自 杭电HDUOJ
题目来源 2013ACM-ICPC杭州赛区全国邀请赛
源链接： HDU-4582
最后修改于 2020-10-25T23:14:52+00:00 由爬虫自动更新
共提交 0 次
通过率 --%
时间上限 内存上限
6000/3000MS(Java/Others) 65535/65536K(Java/Others)