poj2516Minimum Cost

http://poj.org/problem?id=2516

建图的时候 有个地方写错了 卡了半年。。

题意看了N久啊 有N个店主需要K种物品 有M个供应点 每个供应点有K种物品 其实是算K次最小费用 然后叠加 分解开来这题就是求把某种物品从供应点送到店主那里

多个源点-》多个汇点  所以加一个超级源点 和 超级汇点 源点->M个供应点->N个店主->汇点 所以共有m+n+2条边 套最小费用模板就行了

#include <iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<queue>
#define MN 10000
#define MM 10000
#define INF 0xfffffff
using namespace std;
struct node
{
    int u,v,cost,cap,next;
}edge[MM];
int head[MN],t,vis[MN],dist[MN],co[55][55][55],sh[55][55],sto[55][55],pp[MN],flow;
void init()
{
    t = 0;
    memset(head,-1,sizeof(head));
}
void add(int u,int v,int c,int p)
{
    edge[t].u = u;
    edge[t].v = v;
    edge[t].cap = c;
    edge[t].cost = p;
    edge[t].next = head[u];
    head[u] = t++;
    edge[t].v = u;
    edge[t].u = v;
    edge[t].cap = 0;
    edge[t].cost = -p;
    edge[t].next = head[v];
    head[v] = t++;
}
int spfa(int s,int en,int n)
{
    int i,j,u,v;
    for(i =0 ; i <= n ; i++)
    dist[i] = INF;
    memset(vis,0,sizeof(vis));
    memset(pp,-1,sizeof(pp));
    queue<int>q;
    q.push(s);
    vis[s] = 1;
    dist[s] = 0;
    while(!q.empty())
    {
        u = q.front();
        q.pop();
        vis[u] = 0;
        for(i = head[u] ; i != -1 ; i = edge[i].next)
        {
            v = edge[i].v;
            if(edge[i].cap&&dist[v]>dist[u]+edge[i].cost)
            {
                dist[v] = dist[u]+edge[i].cost;
                //cout<<dist[v]<<endl;
                pp[v] = i;
                if(!vis[v])
                {
                    vis[v] = 1;
                    q.push(v);
                }
            }
        }
    }
    //cout<<dist[en]<<" ";
    if(dist[en]==INF)
    return 0;
    return 1;
}
int mcmf(int s,int en,int n)
{
    int i,minf,minc=0;
    while(spfa(s,en,n))
    {
        minf = INF+1;
        for(i = pp[en] ; i != -1 ; i = pp[edge[i].u])
        {
            if(edge[i].cap<minf)
            minf = edge[i].cap;
        }
        flow+=minf;
        for(i = pp[en] ; i != -1 ; i = pp[edge[i].u])
        {
            edge[i].cap-=minf;
            edge[i^1].cap+=minf;
        }
        minc+=minf*dist[en];
    }
    return minc;
}
int main()
{
    int i,j,n,m,k,g;
    while(cin>>n>>m>>k)
    {
        if(n==0&&m==0&&k==0)
        break;
        int flag = 0,ss=0;
        for(i = 1; i <= n ; i++)
            for(j = 1; j <= k ; j++)
                cin>>sh[i][j];
        for(i = 1; i <= m ; i++)
             for(j = 1; j <= k ; j++)
                cin>>sto[i][j];
        for(i = 1;i <= k ; i++)
            for(j = 1 ; j <= n ; j++)
                for(g = 1; g <= m ; g++)
                cin>>co[i][j][g];
        int s = 0,en = n+m+1;
        for(i = 1; i <= k ; i++)
        {
            init();
            int sa=0;
            for(j = 1 ; j <= n ; j++)
            {
               add(m+j,en,sh[j][i],0);
               sa+=sh[j][i];
            }
            for(j = 1; j <= m ; j++)
                add(s,j,sto[j][i],0);
            for(j = 1; j <= m ; j++)
                for(g = 1 ; g <= n ; g++)
                    add(j,m+g,INF,co[i][g][j]);
            flow=0;
            ss+=mcmf(s,en,n+m+1);
            if(sa>flow)
                break;
        }
        if(i==k+1)
        cout<<ss<<endl;
        else
        cout<<"-1\n";
    }
    return 0;
}