[网络流24题] 搭配飞行员（cogs 14）

/*很裸的一道二分图最大匹配*/
#include<cstdio>
#include<iostream>
#define N 110
#define inf 1000000000
using namespace std;
int head[N],dis[N],q[N],n,n1,cnt=1,S,T;
struct node{
    int v,f,pre;
};node e[N*N];
void add(int u,int v,int f){
    e[++cnt].v=v;e[cnt].f=f;e[cnt].pre=head[u];head[u]=cnt;
    e[++cnt].v=u;e[cnt].f=0;e[cnt].pre=head[v];head[v]=cnt;
}
bool bfs(){
    for(int i=1;i<=T;i++)dis[i]=inf;
    int h=0,t=1;q[1]=S;dis[S]=0;
    while(h<t){
        int u=q[++h];
        for(int i=head[u];i;i=e[i].pre){
            int v=e[i].v;
            if(e[i].f&&dis[v]>dis[u]+1){
                dis[v]=dis[u]+1;
                if(v==T)return true;
                q[++t]=v;
            }
        }
    }
    if(dis[T]==inf)return false;
    return true;
}
int dinic(int now,int f){
    if(now==T)return f;
    int rest=f;
    for(int i=head[now];i;i=e[i].pre){
        int v=e[i].v;
        if(e[i].f&&dis[v]==dis[now]+1){
            int t=dinic(v,min(e[i].f,rest));
            if(!t)dis[v]=0;
            e[i].f-=t;
            e[i^1].f+=t;
            rest-=t;
        }
    }
    return f-rest;
}
int main(){
    freopen("flyer.in","r",stdin);
    freopen("flyer.out","w",stdout);
    scanf("%d%d",&n,&n1);
    S=0,T=n+1;
    for(int i=1;i<=n1;i++)add(S,i,1);
    for(int i=n1+1;i<=n;i++)add(i,T,1);
    int x,y;
    while(scanf("%d%d",&x,&y)!=EOF)add(x,y,1);
    int max_flow=0;
    while(bfs())max_flow+=dinic(S,inf);
    printf("%d",max_flow);
    return 0;
}