【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,-1,sizeof(first));en=0;}
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,0,sizeof(inq));
    d[S]=0; inq[S]=1; p[S]=0; a[S]=INF; q.push(S);
    while(!q.empty())
      {
          int U=q.front(); q.pop(); inq[U]=0;
          for(int i=first[U];i!=-1;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]]=1;}
              }
      }
    if(d[T]>2000000000) return 0;
    Flow+=a[T]; Cost+=d[T]*a[T]; int U=T;
    while(U!=S)
      {
          cap[p[U]]-=a[T]; cap[p[U]^1]+=a[T];
          U=u[p[U]];
      }
    return 1;
}
int Mincost()
{
    int Flow=0,Cost=0;
    while(Spfa(Flow,Cost));
    return Cost;
}