FZU 1397 保送

网络流入门题。

源点到每一个学生连一条边，容量为1

每个学校到汇点连一条边，容量为L

符合要求的学生和学校之间连边，容量为1。

从源点到汇点的最大流就是答案。

#include<cstdio>
#include<cstring>
#include<cmath>
#include<vector>
#include<map>
#include<queue>
#include<string>
#include<iostream>
#include<algorithm>
using namespace std;

int tot;
int A,B;
const int maxn = 1000;
const int INF = 0x7FFFFFFF;
struct Edge
{
    int from, to, cap, flow;
    Edge(int u, int v, int c, int f) :from(u), to(v), cap(c), flow(f) {}
};
vector<Edge>edges;
vector<int>G[maxn];
bool vis[maxn];
int d[maxn];
int cur[maxn];
int n, m, s, t;
struct Stu
{
    vector<int>school;
    vector<int>flag;
}stu[500];
struct Sch
{
    bool flag[300+10];
}h[500];

map<string,int>zhuan;

void init()
{
    for (int i = 0; i < maxn; i++) G[i].clear();
    edges.clear();
    s=0;
    t=A+B+1;
    tot=1;
    zhuan.clear();
}

void AddEdge(int from, int to, int cap)
{
    edges.push_back(Edge(from, to, cap, 0));
    edges.push_back(Edge(to, from, 0, 0));
    int w = edges.size();
    G[from].push_back(w - 2);
    G[to].push_back(w - 1);
}
bool BFS()
{
    memset(vis, 0, sizeof(vis));
    queue<int>Q;
    Q.push(s);
    d[s] = 0;
    vis[s] = 1;
    while (!Q.empty())
    {
        int x = Q.front();
        Q.pop();
        for (int i = 0; i<G[x].size(); i++)
        {
            Edge e = edges[G[x][i]];
            if (!vis[e.to] && e.cap>e.flow)
            {
                vis[e.to] = 1;
                d[e.to] = d[x] + 1;
                Q.push(e.to);
            }
        }
    }
    return vis[t];
}
int DFS(int x, int a)
{
    if (x == t || a == 0)
        return a;
    int flow = 0, f;
    for (int &i = cur[x]; i<G[x].size(); i++)
    {
        Edge e = edges[G[x][i]];
        if (d[x]+1 == d[e.to]&&(f=DFS(e.to,min(a,e.cap-e.flow)))>0)
        {
            edges[G[x][i]].flow+=f;
            edges[G[x][i] ^ 1].flow-=f;
            flow+=f;
            a-=f;
            if(a==0) break;
        }
    }
    if(!flow) d[x] = -1;
    return flow;
}
int dinic(int s, int t)
{
    int flow = 0;
    while (BFS())
    {
        memset(cur, 0, sizeof(cur));
        flow += DFS(s, INF);
    }
    return flow;
}

int main()
{
    while(~scanf("%d%d",&A,&B))
    {
        if(!A&&!B) break;
        init();
        

        for(int i=1;i<=A;i++) AddEdge(s,i,1);

        for(int i=1;i<=A;i++)
        {
            int d,p; scanf("%d%d",&d,&p);

            stu[i].flag.clear();
            stu[i].school.clear();
            
            for(int j=1;j<=d;j++)
            {
                string name; cin>>name; 
                if(zhuan[name]==0) {zhuan[name]=tot;tot++;}
                stu[i].flag.push_back(zhuan[name]);
            }
            for(int j=1;j<=p;j++)
            {
                int x; scanf("%d",&x);
                stu[i].school.push_back(x);
            }
        }

        for(int i=1;i<=B;i++)
        {
            int L,F;scanf("%d%d",&L,&F);
            AddEdge(i+A,t,L);
            memset(h[i].flag,0,sizeof h[i].flag);
            for(int j=1;j<=F;j++)
            {
                string name; cin>>name; 
                if(zhuan[name]==0) {zhuan[name]=tot;tot++;}
                h[i].flag[zhuan[name]]=1;
            }
        }

        for(int i=1;i<=A;i++)
        {
            for(int j=0;j<stu[i].school.size();j++)
            {
                int xue=stu[i].school[j];
                for(int k=0;k<stu[i].flag.size();k++)
                    if(h[xue].flag[stu[i].flag[k]])
                        AddEdge(i,A+xue,1);
            }
        }
        printf("%d
",dinic(s,t));
    }

    return 0;
}