[模板] 最小费用最大流

最小费用最大流是十分基础的图论算法，必须掌握 :)

基本思想：增广路+Bellman-Ford

本模板使用的是一个Vector数组G来存储边集。

const int INF=99999999;const int maxn=10005;struct Edge{int from,to,cap,flow,cost;Edge(int u,int v,int c,int f,int w):from(u),to(v),cap(c),flow(f),cost(w) {}};struct MCMF{int n,mvector<Edge> edges;vector<int> G[maxn];int inq[maxn];int d[maxn];int p[maxn];int a[maxn];void init(int n){this->n=n;for(int i=0;i<n;i++){G[i].clear();}edges.clear();}void AddEdge(int from,int to,int cap,int cost){edges.push_back(Edge(from,to,cap,0,cost));edges.push_back(Edge(to,from,0,0,-cost));m=edges.size();G[from].push_back(m-2);G[to].push_back(m-1);}bool BellmanFord(int s,int t,int& flow,long long& 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+=(long long)d[t]*(long long)a[t];for(int u=t;u!=s;u=edges[p[u]].from){edges[p[u]].flow+=a[t];edges[p[u]^1].flow-=a[t];}return true;}int MincostMaxflow(int s,int t,long long &cost){int flow=0;cost=0;while(BellmanFord(s,t,flow,cost));return flow;}}