1569. Networking the “Iset”

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;

}