[SCOI2010]游戏(二分图匹配

#include
using namespace std;
const int N=1e6+10;
vector<int>g[N];
int match[N];
bool vis[N];
ll ans;
int n,m,k;
bool dfs(int x){
	for(int v:g[x]){
		if(vis[v])continue;
		vis[v]=1;
		if(!match[v]||dfs(match[v])){
			match[v]=x;
			return 1;
		}
	}
	return 0;
} 
int main(){
    scanf("%d",&n);
    for(int i=1;i<=n;i++){
        int a,b;scanf("%d%d",&a,&b);
        g[a].push_back(i);
        g[b].push_back(i)
    }
    
    for(int i=1;i<=n;i++){
        memset(vis,0,sizeof vis);
        if(dfs(i)==0){
            cout<<i-1<<endl;
            return 0;
        }
    }
    cout<<n<<endl;
}