标签:style blog http color os for art 问题
费用流即最小费用最大流
先贴上粉书上的模板:
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) {} }; int n,m; vector<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; 粉书上原版有这一句,但明显会报错。感觉去掉也没什么影响... 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) //用队列优化过,感觉和SPFA一样了 { 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 MCMF(int s,int t,long long& cost) //s:起点;t:汇点; { int flow=0; cost=0; //flow:求出来的最大流 cost:求出来的费用 while (BellmanFord(s,t,flow,cost)); return flow; }
Exercise:POJ2516
标签:style blog http color os for art 问题
原文地址:http://www.cnblogs.com/pdev/p/3876547.html