最小费用最大流模板

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 0xfffff
struct 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));
}