Given a simple unweighted graph G (an undirected graph containing no loops nor multiple edges) with n nodes and m edges. Let T be a spanning tree of G.
We say that a cut in G respects T if it cuts just one edges of T.
Since love needs good faith and hypocrisy return for only grief, you should find the minimum cut of graph G respecting the given spanning tree T.
Input
The input contains several test cases.
The first line of the input is a single integer t (1≤t≤5) which is the number of test cases.
Then t test cases follow.
Each test case contains several lines.
The first line contains two integers n (2≤n≤20000) and m (n−1≤m≤200000).
The following n−1 lines describe the spanning tree T and each of them contains two integers u and v corresponding to an edge.
Next m−n+1 lines describe the undirected graph G and each of them contains two integers u and v corresponding to an edge which is not in the spanning tree T.
Output
For each test case, you should output the minimum cut of graph G respecting the given spanning tree T.
Sample Input
1
4 5
1 2
2 3
3 4
1 3
1 4
Sample Output
Case #1: 2
做过类似的题,关键是读错题了。。。
代码:
#include<iostream>
#include<cstdio>
#include<stack>
#include<algorithm>
#include<queue>
#include<cstring>
#include<cmath>
#define maxx 20005
#define maxn 20
using namespace std;
int head[maxx],_next[maxx<<1],to[maxx<<1];
int cnt;
int n,m,N;
void addEdge(int x,int y)
{
to[++cnt]=y,_next[cnt]=head[x],head[x]=cnt;
to[++cnt]=x,_next[cnt]=head[y],head[y]=cnt;
}
int grand[maxx][maxn];
int depth[maxx];
int F[maxx];
void dfs(int root)
{
for(int i=1;i<=N;i++)
grand[root][i]=grand[grand[root][i-1]][i-1];
for(int i=head[root];i;i=_next[i])
{
int v=to[i];
if(v==grand[root][0])
continue;
grand[v][0]=root;
depth[v]=depth[root]+1;
dfs(v);
}
}
int lca(int a,int b)
{
if(depth[a]>depth[b])swap(a,b);
for(int i=N;i>=0;i--)
if(depth[a]<depth[b]&&depth[a]<=depth[grand[b][i]])
b=grand[b][i];
if(a==b)
return a;
for(int i=N;i>=0;i--)
{
if(grand[a][i]!=grand[b][i])
{
a=grand[a][i];
b=grand[b][i];
}
}
return grand[a][0];
}
void dfs2(int root)
{
for(int i=head[root];i;i=_next[i])
{
int v=to[i];
if(v==grand[root][0])
continue;
dfs2(v);
F[root]+=F[v];//累加覆盖数,类似于线性覆盖
}
}
void init()
{
memset(head,0,sizeof(head));
memset(F,0,sizeof(F));
N=floor(log2(n));
depth[1]=0;
cnt=0;
}
int main()
{
int t;
cin>>t;
int cal=1;
while(t--)
{
scanf("%d%d",&n,&m);
init();
int x,y;
for(int i=1;i<n;i++)
{
scanf("%d%d",&x,&y);
addEdge(x,y);
}
dfs(1);
for(int i=n;i<=m;i++)
{
scanf("%d%d",&x,&y);
F[x]++;
F[y]++;
F[lca(x,y)]-=2;
}
dfs2(1);
int ans=m;
for(int i=2;i<=n;i++)
ans=min(ans,F[i]+1);
printf("Case #%d: %d\n",cal++,ans);
}
return 0;
}