Hdu4292 food --- maximum stream

N people, F kinds of food, d kinds of drinks, each have a certain number, each person has their own preferences for each type of food and beverage, must satisfy y at the same time.

How many people can be satisfied.

Add Source Vertex S and sink vertex T.

S to the number of foods with the edge weight.

According to everyone's preferences, food is sent to people, people are sent to drinks, and edge weight is 1.

Each person can only meet the requirements once, so the person is split and connected to his own side, the edge right is 1.

Finally, the edge weight of each type of beverage to T is the number of such drinks.

#include<cstdio>#include<vector>#include<cstring>#include<queue>#define maxn 1010#define inf 0x3f3f3f3fusing namespace std;struct node{    int from,to,cap,flow;};struct dinic{    int n,m,s,t;    vector<node> e;    vector<int> g[maxn];    bool vis[maxn];    int d[maxn];    int cur[maxn];    void init(int n)    {        e.clear();        for(int i=0;i<=n+2;i++)            g[i].clear();    }    void addedge(int a,int b,int c,int d)    {        e.push_back((node){a,b,c,0});        e.push_back((node){b,a,d,0});        m=e.size();        g[a].push_back(m-2);        g[b].push_back(m-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++)            {                node& ee=e[g[x][i]];                if(!vis[ee.to]&&ee.cap>ee.flow)                {                    vis[ee.to]=1;                    d[ee.to]=d[x]+1;                    q.push(ee.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++)        {            node& ee=e[g[x][i]];            if(d[x]+1==d[ee.to]&&(f=dfs(ee.to,min(a,ee.cap-ee.flow)))>0)            {                ee.flow+=f;                e[g[x][i]^1].flow-=f;                flow+=f;                a-=f;                if(a==0) break;            }        }        return flow;    }    int maxflow(int s,int t)    {        this->s=s;        this->t=t;        int flow=0;        while(bfs())        {            memset(cur,0,sizeof cur);            flow+=dfs(s,inf);        }        return flow;    }};dinic solve;int main(){    int i,j,a,n,f,d,s,t;    char str[210];    while(~scanf("%d%d%d",&n,&f,&d))    {        s=0,t=f+n+n+d+1;        solve.init(t);        for(i=1;i<=f;i++)        {            scanf("%d",&a);            solve.addedge(s,i,a,0);        }        for(i=f+1;i<=f+n;i++) solve.addedge(i,i+n,1,0);        for(i=1;i<=d;i++)        {            scanf("%d",&a);            solve.addedge(i+n+n+f,t,a,0);        }        for(i=1;i<=n;i++)        {            scanf("%s",str);            for(j=1;j<=f;j++) if(str[j-1]=='Y')                solve.addedge(j,f+i,1,0);        }        for(i=1;i<=n;i++)        {            scanf("%s",str);            for(j=1;j<=d;j++) if(str[j-1]=='Y')                solve.addedge(f+n+i,f+n+n+j,1,0);        }        printf("%d\n",solve.maxflow(s,t));    }    return 0;}

Hdu4292 food --- maximum stream