提供一個費用流的模板

bool spfa(int s,int t){int i,tt;int inq[3000];memset(inq,0,sizeof(inq));memset(p,-1,sizeof(p));memset(pre,-1,sizeof(pre));for(i=0;i<=t;i++) d[i]=inf;d[s]=0;queue<int> q;q.push(s);while(!q.empty()){int u=q.front();q.pop();inq[u]=0;for(tt=H[u];~tt;tt=a[tt].next){if(a[tt].c){int v=a[tt].v;if(d[v]>d[u]+a[tt].w){d[v]=d[u]+a[tt].w;p[v]=u;pre[v]=tt;if(!inq[v]){inq[v]=1;q.push(v);}}}}}if(d[t]>=inf)return false;elsereturn true;}void MCMF(int s,int t){ans_cost=0,ans_flow=0;while(spfa(s,t)){int u=t;int delta=inf;while(p[u]!=-1){delta=min(delta,a[pre[u]].c);u=p[u];}u=t;while(p[u]!=-1){a[pre[u]].c-=delta;a[pre[u]^1].c+=delta;u=p[u];}ans_cost+=delta*d[t];ans_flow+=delta;}}