hdu 3849 (双联通求桥)

一道简单的双联通求桥的题目，，数据时字符串，，map用的不熟练啊，，，，，，，，，，，，，

 

#include <iostream>

#include <cstring>

#include <cstdio>

#include <map>

#include <string>

#include <algorithm>

#define N 10001

using namespace std;

int head[N],num,dfs[N],low[N],n,m,idx,bridge[N],bum;

struct edge

{

	int st,ed,next;

}E[N*20];

void addedge(int x,int y)

{

	E[num].st=x;

	E[num].ed=y;

	E[num].next=head[x];

	head[x]=num++;

}

int cmp(const void *a,const void *b)

{

    return *(int *)a-*(int *)b;

}

void Tarjan(int u,int father)

{

    int i,v;

    low[u]=dfs[u]=idx++;

    for(i=head[u];i!=-1;i=E[i].next)

    {

        v=E[i].ed;

        if(v==father)continue;

        if(dfs[v]==-1)

        {

            Tarjan(v,u);

            low[u]=low[u]>low[v]?low[v]:low[u];

            if(low[v]>dfs[u])//桥

            {

				bridge[bum++]=i;

            }

        }

        else low[u]=low[u]>dfs[v]?dfs[v]:low[u];

    }

}

int main()

{

	int i,x,y,j,t,sum;

	char str[2][200];

	scanf("%d",&t);

	while(t--)

    {

        scanf("%d%d",&n,&m);

		memset(head,-1,sizeof(head));

		num=0;sum=1;

		map<string,int>mp;

        map<int,string>mmp;

		for(i=0;i<m;i++)

		{

			scanf("%s%s",str[0],str[1]);

			if(mp[str[0]]==0)

			{

				mp[str[0]]=sum;

				mmp[sum]=str[0];

				sum++;

			}

			if(mp[str[1]]==0)

			{

				mp[str[1]]=sum;

				mmp[sum]=str[1];

				sum++;

			}

			x=mp[str[0]];

			y=mp[str[1]];

			addedge(x,y);

			addedge(y,x);

		}

		memset(dfs,-1,sizeof(dfs));

		idx=0;

		bum=0;

		Tarjan(1,-1);

		for(i=1;i<=n;i++)

        {

            if(dfs[i]==-1)

                break;

        }

        if(i<=n){printf("0\n");continue;}

		printf("%d\n",bum);

		qsort(bridge,bum,sizeof(bridge[0]),cmp);

		for(j=0;j<bum;j++)

        {

            i=bridge[j];

            i=(i/2*2);

            x=E[i].st;

            y=E[i].ed;

            if(x!=y)

                printf("%s %s\n",mmp[E[i].st].c_str(),mmp[E[i].ed].c_str());

        }

	}

	return 0;

}