最小费用最大流模板

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BellmanFord 沿最短路增广

注意网络中不能有负权圈但是存在负权的边是可以的

#include<stdio.h>#include<iostream>#include<string.h>#include<vector>#include<queue>#include<algorithm>using namespace std;#define maxn 1005#define inf  0xfffffstruct Edge{    int from,to,cap,flow;    int cost;};struct MCMF{    int n,m,s,t;    vector<Edge> edges;    vector<int> G[maxn];    int inq[maxn];    int d[maxn];    int p[maxn];    int a[maxn];    void init(int n)    {        for(int i=0;i<n;++i)        {            G[i].clear();        }        edges.clear();    }    void AddEdge(int from,int to,int cap,int flow,int cost)    {        edges.push_back((Edge){from,to,cap,0,cost});        edges.push_back((Edge){to,from,0,0,-cost});        m = (int )edges.size();        G[from].push_back(m-2);        G[to].push_back(m-1);            }   bool BF(int s,int t, int &flow,int &cost)     {       for(int i=0;i<n;++i){d[i]=inf;}         memset(inq,0,sizeof inq);         d[s]=0;inq[s]=1;p[s]=0;a[s]=inf;         queue<int>Q;         Q.push(s);         while(!Q.empty())         {             int u=Q.front();             Q.pop();             inq[u]=0;             for(int i=0;i<G[u].size();++i)             {                 Edge &e= edges[G[u][i]];                 if(e.cap>e.flow&&d[e.to]>d[u]+e.cost)                 {                     d[e.to]=d[u]+e.cost;                     p[e.to]=G[u][i];                     a[e.to]=min(a[u],e.cap-e.flow);                     if(!inq[e.to]){Q.push(e.to);inq[e.to]=1;}                 }             }         }         if(d[t]==inf){return false;}         flow+=a[t];         cost+=d[t]*a[t];         int u=t;         while(u!=s)         {             edges[p[u]].flow+=a[t];             edges[p[u]^1].flow-=a[t];             u=edges[p[u]].from;         }         return true;     }    int Mincost(int s,int t)    {        int flow=0,cost=0;        while(BF(s,t,flow,cost));        return cost;    }};int main(){    MCMF mc;    scanf("%d",&mc.n);        mc.AddEdge(0,1,2,3,4);    printf("%d\n",mc.Mincost(0,1));}

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