[图论] hdu 3836 Equivalent Sets

/**
[图论] hdu 3836 Equivalent Sets
求一个图中至少添加几条边成为强连通。
跑一遍tarjan缩点,统计0出度和0入度的点数x,y，则ans = max(x,y)
*/
#include <stdio.h>
#include <vector>
#include <string.h>
#include <algorithm>
using namespace std;
#define N 20002

vector<int> vec[N];
int stop,cnt,scnt,id[N],pre[N],low[N],s[N],in[N],out[N];

void tarjan(int v,int n)
{
    int t,minc = low[v] = pre[v] = cnt++;
    vector<int>::iterator pv;
    s[stop++] = v;
    for(pv =  vec[v].begin(); pv != vec[v].end(); ++pv)
    {
        if(-1 == pre[*pv])
            tarjan(*pv,n);
        if(low[*pv] < minc)
            minc = low[*pv];
    }
    if(minc < low[v])
    {
        low[v] = minc;
        return ;
    }
    do{
        id[t = s[--stop] ]  = scnt;
        low[t] =