UESTC 900 方老师炸弹 --Tarjan求割点及删点后连通分量数

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <vector>
#define Mod 1000000007
using namespace std;
#define N 10007

vector<int> G[N];
struct CUT
{
    int v,num;
}cut[N];
int vis[N],dfn[N],low[N],Time;
int n,m,k;

int cmp(CUT ka,CUT kb)
{
    if(ka.num == kb.num)
        return ka.v < kb.v;
    return ka.num > kb.num;
}

void Tarjan(int u,int fa)
{
    low[u] = dfn[u] = ++Time;
    int cnt = 0;
    vis[u] = 1;
    int flag = 1;
    for(int i=0;i<G[u].size();i++)
    {
        int v = G[u][i];
        if(v == fa && flag)  //重边
        {
            flag = 0;
            continue;
        }
        if(!vis[v])    //树边
        {
            Tarjan(v,u);
            cnt++;
            low[u] = min(low[u],low[v]);
            if(low[v] >= dfn[u])
                cut[u].num++;
        }
        else if(vis[v] == 1)   //回边
            low[u] = min(low[u],dfn[v]);
    }
    if(fa == -1 && cnt == 1)  //为根且度数为1，不是割点
        cut[u].num = 1;
    vis[u] = 2;
    return;
}

int main()
{
    int i,j,u,v;
    while(scanf("%d%d%d",&n,&m,&k)!=EOF)
    {
        Time = 0;
        for(i=0;i<=n;i++)
        {
            G[i].clear();
            cut[i].v = i;
            cut[i].num = 1;
        }
        cut[0].num = 0;    //根要特判
        while(m--)
        {
            scanf("%d%d",&u,&v);
            G[u].push_back(v);
            G[v].push_back(u);
        }
        memset(dfn,0,sizeof(dfn));
        memset(low,0,sizeof(low));
        memset(vis,0,sizeof(vis));
        Tarjan(0,-1);
        sort(cut,cut+n,cmp);
        for(i=0;i<k;i++)
            printf("%d %d\n",cut[i].v,cut[i].num);
        printf("\n");
    }
    return 0;
}