Redundant Paths POJ - 3177

​​点击打开链接​​

边双连通分量模板 两个版本

第一个改自kuangbin模板 第二个自己xjb写的 感觉点与边双连通分量都没必要写单独的模板 求出割点与割边再dfs就好

#include <stdio.h>
#include <stack>
#include <cstring>
#include <algorithm>
using namespace std;

struct node
{
    int v;
    int next;
    int flag;
};

stack <int> stk;
node edge[20010];
int first[5010],dfn[5010],low[5010],book[5010],belong[5010],degree[5010];
int n,m,num,cnt1,cnt2,ans;

void addedge(int u,int v)
{
    edge[num].v=v;
    edge[num].next=first[u];
    edge[num].flag=0;
    first[u]=num++;
    return;
}

void dfs(int u,int fa)
{
    int i,v;
    stk.push(u);
    num++;
    dfn[u]=num;
    low[u]=num;
    book[u]=1;
    for(i=first[u];i!=-1;i=edge[i].next)
    {
        v=edge[i].v;
        if(v==fa) continue;
        if(dfn[v]==0)
        {
            dfs(v,u);
            if(low[u]>low[v])
            {
                low[u]=low[v];
            }
            if(low[v]>dfn[u])
            {
                cnt1++;
                edge[i].flag=1;
                edge[i^1].flag=1;
            }
        }
        else if(book[v]==1&&low[u]>dfn[v])
        {
            low[u]=dfn[v];
        }
    }
    if(dfn[u]==low[u])
    {
        cnt2++;
        while(!stk.empty())
        {
            v=stk.top();
            stk.pop();
            book[v]=0;
            belong[v]=cnt2;
            if(u==v) break;
        }
    }
    return;
}

void tarjan()
{
    int i,j;
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(book,0,sizeof(book));
    memset(belong,0,sizeof(belong));
    memset(degree,0,sizeof(degree));
    num=0,cnt1=0,cnt2=0;
    for(i=1;i<=n;i++)
    {
        if(dfn[i]==0)
        {
            dfs(i,-1);
        }
    }
    for(i=1;i<=n;i++)
    {
        for(j=first[i];j!=-1;j=edge[j].next)
        {
            if(edge[j].flag==1)
            {
                degree[belong[i]]++;
            }
        }
    }
    ans=0;
    for(i=1;i<=cnt2;i++)
    {
        if(degree[i]==1) ans++;
    }
    return;
}

int main()
{
    int i,u,v;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        memset(first,-1,sizeof(first));
        num=0;
        for(i=1;i<=m;i++)
        {
            scanf("%d%d",&u,&v);
            addedge(u,v);
            addedge(v,u);
        }
        tarjan();
        printf("%d\n",(ans+1)/2);
    }
    return 0;
}

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

struct node
{
    int v;
    int next;
    int flag;
};

node edge[20010];
int first[5010],dfn[5010],low[5010],book[5010],belong[5010],degree[5010];
int n,m,num,tot;

void addedge(int u,int v)
{
    edge[num].v=v;
    edge[num].next=first[u];
    edge[num].flag=0;
    first[u]=num++;
    return;
}

void dfsI(int cur,int pre)
{
    int cnt,i,v;
    num++;
    dfn[cur]=num,low[cur]=num;
    cnt=0;
    for(i=first[cur];i!=-1;i=edge[i].next)
    {
        v=edge[i].v;
        if(!dfn[v])
        {
            dfsI(v,cur);
            low[cur]=min(low[cur],low[v]);
            if(low[v]>dfn[cur])
            {
                edge[i].flag=1;
                edge[i^1].flag=1;
            }
        }
        else if(v==pre)
        {
            if(cnt>0) low[cur]=min(low[cur],dfn[v]);
            cnt++;
        }
        else
        {
            low[cur]=min(low[cur],dfn[v]);
        }
    }
    return;
}

void dfsII(int cur)
{
    int i,v;
    for(i=first[cur];i!=-1;i=edge[i].next)
    {
        v=edge[i].v;
        if(!edge[i].flag&&!book[v])
        {
            book[v]=1;
            belong[v]=tot;
            dfsII(v);
        }
    }
    return;
}

void tarjan()
{
    int i,u,v,ans;
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    num=0;
    for(i=1;i<=n;i++)
    {
        if(!dfn[i]) dfsI(i,-1);
    }
    memset(book,0,sizeof(book));
    memset(belong,0,sizeof(belong));
    memset(degree,0,sizeof(degree));
    tot=0;
    for(i=1;i<=n;i++)
    {
        if(!book[i])
        {
            book[i]=1;
            belong[i]=++tot;
            dfsII(i);
        }
    }
    for(u=1;u<=n;u++)
    {
        for(i=first[u];i!=-1;i=edge[i].next)
        {
            v=edge[i].v;
            if(belong[u]!=belong[v])
            {
                degree[belong[u]]++,degree[belong[v]]++;
            }
        }
    }
    ans=0;
    for(i=1;i<=tot;i++)
    {
        if(degree[i]==2) ans++;
    }
    printf("%d\n",(ans+1)/2);
    return;
}

int main()
{
    int i,u,v;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        memset(first,-1,sizeof(first));
        num=0;
        for(i=1;i<=m;i++)
        {
            scanf("%d%d",&u,&v);
            addedge(u,v);
            addedge(v,u);
        }
        tarjan();
    }
    return 0;
}