bzoj1143: [CTSC2008]祭祀river

#include<cstdio>
#include<cstring>
#include<cctype>
#include<algorithm>
#include<bitset>
using namespace std;
#define rep(i,s,t) for(int i=s;i<=t;i++)
#define dwn(i,s,t) for(int i=s;i>=t;i--)
#define clr(x,c) memset(x,c,sizeof(x))
#define qwq(x) for(edge *o=head[x];o;o=o->next)
int read(){
    int x=0;char c=getchar();
    while(!isdigit(c)) c=getchar();
    while(isdigit(c)) x=x*10+c-‘0‘,c=getchar();
    return x;
}
const int nmax=105;
const int maxn=10005;
const int inf=0x7f7f7f7f;
struct edge{
    int to;edge *next;
};
edge es[maxn],*pt=es,*head[nmax];
void add(int u,int v){
    pt->to=v;pt->next=head[u];head[u]=pt++;
}
bitset<nmax>vis;
int match[nmax],dis[nmax][nmax];
bool dfs(int x){
    qwq(x) if(!vis[o->to]) {
        vis[o->to]=1;
        if(!match[o->to]||dfs(match[o->to])) {
            match[o->to]=x;return true;
        }
    }
    return false;
}
int main(){
    int n=read(),m=read(),u,v;
    rep(i,1,m) u=read(),v=read(),dis[u][v]=1;
    rep(i,1,n) rep(j,1,n) rep(k,1,n) dis[j][k]|=(dis[j][i]&dis[i][k]);
    rep(i,1,n) rep(j,1,n) if(i!=j&&dis[i][j]) add(i,j);
    int ans=n;
    rep(i,1,n) {
        vis.reset();
        if(dfs(i)) ans--;
    }
    printf("%d\n",ans);
    return 0;
}