http://acm.timus.ru/problem.aspx?space=1&num=1569
枚举每一个点为起点 进行广搜 比较每次搜到的树 选择最优的一种结果
代码:
#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<map>
#include<vector>
#include<stack>
#include<set>
#include<map>
#include<queue>
#include<algorithm>
#include<cmath>
#define LL long long
//#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;
const int INF=0x3f3f3f3f;
const int N=205;
const int M=200005;
int l[M],r[M];
bool instal[M],tmp[M];
int head[N],I;
struct node
{
int j,next;
int k;
}edge[M];
int dist[N];
bool final[N];
int D;
int n,m;
void add(int i,int j,int k)
{
edge[I].j=j;
edge[I].k=k;
edge[I].next=head[i];
head[i]=I++;
}
void bfs(int x1)
{
memset(final,true,sizeof(final));
memset(dist,-1,sizeof(dist));
memset(tmp,false,sizeof(tmp));
queue<int>qt;
qt.push(x1);
dist[x1]=0;
while(!qt.empty())
{
int x=qt.front();
qt.pop();
for(int t=head[x];t!=-1;t=edge[t].next)
{
int j=edge[t].j;
if(dist[j]==-1)
{
final[x]=false;
dist[j]=dist[x]+1;
//cout<<edge[t].k<<endl;
tmp[edge[t].k]=true;
qt.push(j);
}
}
}
int k1=-1,k2=-1;
for(int i=1;i<=n;++i)
if(final[i])
{
if(k2==-1||dist[i]>dist[k2])
k2=i;
if(k1==-1||dist[k2]>dist[k1])
swap(k1,k2);
}
int d=0;
if(k1!=-1)
d+=dist[k1];
if(k2!=-1)
d+=dist[k2];
if(D==-1||d<D)
{//cout<<d<<" "<<D<<endl;
D=d;
for(int i=1;i<=m;++i)
instal[i]=tmp[i];
}
}
int main()
{
//freopen("data.in","r",stdin);
while(cin>>n>>m)
{
memset(head,-1,sizeof(head));
I=0;
D=-1;
for(int i=1;i<=m;++i)
{
cin>>l[i]>>r[i];
add(l[i],r[i],i);
add(r[i],l[i],i);
}
for(int i=1;i<=n;++i)
bfs(i);
for(int i=1;i<=m;++i)
if(instal[i])
cout<<l[i]<<" "<<r[i]<<endl;
}
return 0;
}
转载于:https://www.cnblogs.com/liulangye/archive/2013/01/26/2878175.html