【费用流】【Next Array】费用流模板(spfa版)

 #include<cstdio>
 #include<algorithm>
 #include<cstring>
 #include<queue>
 using namespace std;
 #define MAXN 501
 #define MAXM 50001
 #define INF 2147483647
 int S,T,n,m;
 int en,u[MAXM],v[MAXM],first[MAXN],next[MAXM],cap[MAXM],cost[MAXM];//Next Array
 bool inq[MAXN];
 int d[MAXN]/*spfa*/,p[MAXN]/*spfa*/,a[MAXN]/*可改进量*/;
 queue<int>q;
 void Init_MCMF(){memset(first,-,sizeof(first));en=;}
 void AddEdge(const int &U,const int &V,const int &W,const int &C)
 {
     u[en]=U; v[en]=V; cap[en]=W; cost[en]=C;
     next[en]=first[U]; first[U]=en++;
     u[en]=V; v[en]=U; cap[en]=0; cost[en]=-C;
     next[en]=first[V]; first[V]=en++;
 }
 bool Spfa(int &Flow,int &Cost)
 {
     memset(d,0x7f,sizeof(d));
     memset(inq,,sizeof(inq));
     d[S]=; inq[S]=; p[S]=; a[S]=INF; q.push(S);
     while(!q.empty())
       {
           int U=q.front(); q.pop(); inq[U]=;
           for(int i=first[U];i!=-;i=next[i])
             if(cap[i] && d[v[i]]>d[U]+cost[i])
               {
                 d[v[i]]=d[U]+cost[i];
                 p[v[i]]=i;
                 a[v[i]]=min(a[U],cap[i]);
                 if(!inq[v[i]]) {q.push(v[i]); inq[v[i]]=;}
               }
       }
     if(d[T]>) return ;
     Flow+=a[T]; Cost+=d[T]*a[T]; int U=T;
     while(U!=S)
       {
           cap[p[U]]-=a[T]; cap[p[U]^]+=a[T];
           U=u[p[U]];
       }
     return ;
 }
 int Mincost()
 {
     int Flow=,Cost=;
     while(Spfa(Flow,Cost));
     return Cost;
 }