The King’s Problem 强连通

#include<bits/stdc++.h>
#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
//input by bxd
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define repp(i,a,b) for(int i=(a);i>=(b);--i)
#define RI(n) scanf("%d",&(n))
#define RII(n,m) scanf("%d%d",&n,&m)
#define RIII(n,m,k) scanf("%d%d%d",&n,&m,&k)
#define RS(s) scanf("%s",s);
#define ll long long
#define pb push_back
#define REP(i,N)  for(int i=0;i<(N);i++)
#define CLR(A,v)  memset(A,v,sizeof A)
//////////////////////////////////
#define inf 0x3f3f3f3f
const int N=5000+5;
int head[20*N],pos;
struct Edge
{
    int to,nex;
}edge[20*N];
void add(int a,int b)
{
    edge[++pos].nex=head[a];
    head[a]=pos;
    edge[pos].to=b;
}
int low[N],dfn[N],inde,Stack[N],vis[N],tot,cnt,belong[N],out[N];

vector<int>G[N];
int used[N];
void init()
{
    CLR(dfn,0);
    CLR(vis,0);
    CLR(low,0);
    CLR(out,0);
    pos=inde=tot=cnt=0;
    CLR(head,0);

}
void tarjan(int x)
{
    dfn[x]=low[x]=++tot;
    Stack[++inde]=x;
    vis[x]=1;
    for(int i=head[x];i;i=edge[i].nex)
    {
        int v=edge[i].to;
        if(!dfn[v])
        {
            tarjan(v);
            low[x]=min(low[x],low[v]);
        }
        else if(vis[v])
        low[x]=min(low[x],low[v]);
    }
    if(dfn[x]==low[x])
    {
        cnt++;int v;
        do
        {
            v=Stack[inde--];
            vis[v]=0;
            belong[v]=cnt;
        }
        while(v!=x);
    }
}

bool dfs(int x)
{
    if(G[x].size())
    rep(j,0,G[x].size()-1)
    {
        int t=G[x][j];
        if(!used[t])
        {
            used[t]=1;
            if(!vis[t]||dfs(vis[t]))
            {
                vis[t]=x;
                return true;
            }
        }
    }
    return false;
}

int find1(void )
{
    int ans=0;
    CLR(vis,0);
    rep(i,1,cnt)
    {
        CLR(used,0);
        if(dfs(i))ans++;
    }
    return ans;
}

int main()
{
    int cas;
    RI(cas);
    while(cas--)
    {
        
        int n,m;
        RII(n,m);
        rep(i,1,m)
        {
            int a,b;RII(a,b);
            add(a,b);
        }
        rep(i,1,n)
        if(!dfn[i])
        tarjan(i);
        rep(i,1,n)
        {
            int u=belong[i];
            for(int j=head[i];j;j=edge[j].nex)
            {
                int v=belong[ edge[j].to ];
                if(u!=v)
                    G[u].pb(v);
            }
        }
        cout<<cnt-find1()<<endl;
        rep(i,1,cnt)
        G[i].clear();
        init();
    }
    return 0;
}