二分图应用模版
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cstdlib>
#include <queue>
using namespace std;
const int MAXN=400,MAXM=50005;
int head[MAXN],nume,n,m,maxflow,s,t,cur[MAXN],dep[MAXN];
queue<int>q;
struct edge{
int to,nxt,cap,flow;
}e[MAXM];
void adde(int from,int to,int cap){
e[++nume].to=to;
e[nume].cap=cap;
e[nume].nxt=head[from];
head[from]=nume;
}
bool bfs(){
memset(dep,0,sizeof(dep));
q.push(s);dep[s]=1;
while(!q.empty()){
int u=q.front();q.pop();
for(int i=head[u];i;i=e[i].nxt){
int v=e[i].to;
if(!dep[v]&&e[i].flow<e[i].cap){
dep[v]=dep[u]+1;
q.push(v);
}
}
}
return dep[t];
}
int dfs(int u,int flow){
if(u==t) return flow;
int tot=0;
for(int &i=cur[u];i&&tot<flow;i=e[i].nxt){
int v=e[i].to;
if(dep[v]==dep[u]+1&&e[i].flow<e[i].cap){
if(int t=dfs(v,min(flow-tot,e[i].cap-e[i].flow))){
e[i].flow+=t;
e[((i-1)^1)+1].flow-=t;
tot+=t;
}
}
}
return tot;
}
void dinic(){
while(bfs()){
for(int i=s;i<=t;i++) cur[i]=head[i];
maxflow+=dfs(s,0x3f3f3f3f);
}
}
bool f[MAXN];
void print(int u){
printf("%d ",u);
f[u]=1;
for(int i=head[u];i;i=e[i].nxt){
int v=e[i].to;
if(v&&!f[v-n]&&e[i].flow){
print(v-n);
return;
}
}
}
int main(){
cin>>n>>m;
s=0;t=n*2+1;
for(int i=1;i<=m;i++){
int u,v;
scanf("%d%d",&u,&v);
adde(u,v+n,1);adde(v+n,u,0);
}
for(int i=1;i<=n;i++){
adde(s,i,1);adde(i,s,0);
adde(i+n,t,1);adde(t,i+n,0);
}
dinic();
for(int i=1;i<=n;i++){
if(!f[i]) print(i),printf("\n");
}
printf("%d\n",n-maxflow);
}