点双连通分量之割点
http://www.cnblogs.com/en-heng/p/4002658.html
这篇说得相当清楚
http://blog.csdn.net/fuyukai/article/details/51039788
我大概是个辣鸡吧
/(ㄒoㄒ)/~~
一会整个自己的板子弄上来估计就稳了
一会分析一下板子
放模板题
点双连通分量
POJ - 1523

喵喵喵
#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
#include<math.h>
#include<map>
using namespace std;
const int maxn = 1005;
bool vis[maxn];
int dfn[maxn],low[maxn],subnet[maxn];
int head[maxn];

int cnt, m ,index ,son;
struct edge
{
    int v,next;
}e[maxn];
 
void add(int u, int v)
{
    e[cnt].v= v;
    e[cnt].next = head[u];
    head[u] = cnt++;
}

void init()
{
    m = son = cnt = 0;
    index = 1;
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(subnet,0,sizeof(subnet));
    memset(vis,false,sizeof(vis));
    memset(head,-1,sizeof(head)); 
}

void Tarjan(int u)
{
    vis[u] = true;
    for(int i = head[u];i!=-1;i = e[i].next)
    {
        int v = e[i].v;
        if(!vis[v])
        {
            index++;
            low[v] = dfn[v] = index;
            Tarjan(v);
            low[u] = min(low[u], low[v]);
            if(low[v] >= dfn[u])
            {
                u==1? son++ : subnet[u]++;
            }
        }
        else
        {
            low[u] = min(low[u],dfn[v]);
        }
    }
}

int main()
{
    int u,v,ca = 1;
    while(scanf("%d",&u)!=EOF && u)
    {
        init();
        scanf("%d",&v);
        add(u,v);
        add(v,u);
        m = max(m,max(u,v));
        while(scanf("%d",&u)!=EOF && u)
        {
            scanf("%d",&v);
            add(u,v);
            add(v,u);
            m = max(m,max(u,v));
        }
        Tarjan(1);
        if(son > 1)
        {
            subnet[1] = son-1;
        } 
        printf("Network #%d\n",ca++);
        bool flag = false;
        for(int i=1;i<=m;i++)
        {
            if(subnet[i])
            {
                flag = true;
                printf("  SPF node %d leaves %d subnets\n",i,subnet[i]+1);
            }
        }
        if(!flag)
        {
            printf("  No SPF nodes\n");
        }
        printf("\n");
    }
} 

边双连通分量
POJ - 3352

喵喵喵
#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
#include<math.h>
#include<map>
using namespace std;
const int maxn = 1005;
struct node
{
    int to,next;
} edge[maxn*5];
int head[maxn],dfn[maxn],low[maxn],stack[maxn],cou[maxn];
int n,m,time,cnt,top;
bool vis[maxn];
void init()
{
    memset(vis,0,sizeof(vis));
    memset(head,-1,sizeof(head));
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(cou,0,sizeof(cou));
    top = cnt = 0;
    time = 1;
}

void addedge(int u, int v)
{
    edge[cnt].to = v;
    edge[cnt].next = head[u];
    head[u] = cnt;
    cnt++;
}
void dfs(int u,int fa)
{
    dfn[u] = low[u] = time++;
    vis[u] = true;
    stack[top++] = u;
    for(int i = head[u];i!=-1;i=edge[i].next)
    {
        int v = edge[i].to;
        if(v!=fa && dfn[u] > dfn[v])
        {
            if(!vis[v])
            {
                dfs(v,u);
                low[u] = min(low[u],low[v]);
            }
            else
            {
                low[u] = min(low[u], dfn[v]);
            }
        }
    }
    if(dfn[u] == low[u])
    {
        while(stack[top] != u && top>0)
        {
            low[stack[top-1]] = low[u];
            top--;
            vis[stack[top]] = false;
        }
    }
}
int main()
{
    int u,v;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        init();
        for(int i=0;i<m;i++)
        {
            scanf("%d%d",&u,&v);
            u--;
            v--;
            addedge(u,v);
            addedge(v,u);
        }
        dfs(0,-1);
        for(int i=0;i<n;i++)
        {
            for(int j=head[i]; j!=-1;j=edge[j].next)
            {
                if(low[i] != low[edge[j].to])
                {
                    cou[low[i]]++;
                    cou[low[edge[j].to]] ++;
                }
            }
        }
        cnt = 0;
        for(int i=0;i<=n;i++)
        {
            if(cou[i]/2==1) cnt++;
        }
        printf("%d\n",(cnt+1)/2);
    }
 }