POJ

题目链接 ： POJ1149

画出最初的模型，想办法化简。

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
#include <iostream>
#include <queue>
using namespace std;
#define next Next
const int inf = 0x3f3f3f3f;
const int maxn=205;
int level[maxn];
int iter[maxn];
int head[maxn],tot;
struct edge{
    int to,cap,Next;
} e[20005]; ///此处应为边的两倍，加一条容量为0的反向边
void init(){
    memset(head,-1,sizeof(head));
    tot=0;
}
void add(int from,int to,int cap){
    e[tot].Next=head[from];
    e[tot].to=to;
    e[tot].cap=cap;
    head[from]=tot;
    tot++;
}
void addedge(int from,int to,int cap){
    add(from,to,cap);
    add(to,from,0);
}
void bfs(int s){
    memset(level,-1,sizeof(level));
    queue<int> q;
    level[s]=0;
    q.push(s);
    while(!q.empty()){
        int v=q.front(); q.pop();
        for(int i=head[v];~i;i=e[i].Next){
            edge &ed=e[i];
            if(ed.cap>0&&level[ed.to]<0){
                level[ed.to]=level[v]+1;
                q.push(ed.to);
            }
        }
    }
}
int dfs(int v,int t,int f){
    if(v==t) return f;
    for(int &i=iter[v];~i;i=e[i].Next){
        edge &ed=e[i];
        if(ed.cap>0&&level[v]<level[ed.to]){
            int d=dfs(ed.to,t,min(f,ed.cap));
            if(d>0){
                ed.cap-=d;
                e[i^1].cap+=d;
                return d;
            }
        }
    }
    return 0;
}
int max_flow(int s,int t){
    int flow=0;
    while(1){
        bfs(s);
        if(level[t]<0) return flow;
        memcpy(iter,head,sizeof(iter));
        int f;
        while((f=dfs(s,t,inf))>0){
            flow+=f;
        }
    }
}

vector<int> customer[1005];
int pig[1005];
int main()
{
    int n,m;
    init();
    scanf("%d %d",&m,&n);
    int s = n+1;
    int t = n+2;
    for(int i=1;i<=m;i++) scanf("%d",&pig[i]);
    for(int i=1;i<=n;i++)
    {
        int a,x,b;
        scanf("%d",&a);
        for(int j=1;j<=a;j++)
        {
            scanf("%d",&x);
            customer[x].push_back(i);
        }
        scanf("%d",&b);
        addedge(i,t,b);
    }
    for(int i=1;i<=m;i++)
    {
        int tt = customer[i].size();
        for(int j=0;j<tt;j++)
        {
            if(j==0)
            {
                addedge(s,customer[i][0],pig[i]);
            }
            if(j+1<tt)
            addedge(customer[i][j],customer[i][j+1],inf);
        }
    }
    int ans = max_flow(s,t);
    printf("%d
",ans);
    return 0;
}