最小费用最大流

#include<stdio.h> 

 #include<string.h> 

 #include<queue> 

 #include<algorithm> 

 #include<iostream> 

 using namespace std; 

 #define maxn 550 

 #define INF 99999999 



 int prev[maxn]; 

 bool vis[maxn]; 

 int head[maxn]; 

 int ep,flow; 

 int Dist[maxn]; 

 struct ele 

 { 

     int u; 

     int v; 

     int w; 

     int c; 

     int next; 

 }edge[200*maxn]; 



 void Add(int u,int v,int w,int c) 

 { 

     edge[ep].u=u; 

     edge[ep].v=v; 

     edge[ep].w=w; 

     edge[ep].c=c; 

     edge[ep].next=head[u]; 

     head[u]=ep++; 

     edge[ep].u=v; 

     edge[ep].v=u; 

   
   edge[ep].w=-w;
     edge[ep].c=0; 

     edge[ep].next=head[v]; 

     head[v]=ep++; 

 } 



 int spfa(int S,int E) 

 { 

     int i; 

     int v; 

     queue<int>Q; 

     int u; 

     for(i=0;i<maxn;i++) 

     { 

         Dist[i]=INF; 

         prev[i]=-1; 

         vis[i]=false; 

     } 

     vis[S]=true; 

     Dist[S]=0; 



     Q.push(S); 

     while(!Q.empty()) 

     { 

         u=Q.front(); 

         Q.pop(); 

         vis[u]=false; 

         for(i=head[u];i!=-1;i=edge[i].next) 

         { 

             v=edge[i].v; 

             if(edge[i].c&&Dist[u]+edge[i].w<Dist[v]) 

             { 

                 Dist[v]=Dist[u]+edge[i].w; 

                 prev[v]=i; 

                 if(!vis[v])//记录的为点 

                 { 

                     Q.push(v); 

                     vis[v]=true; 

                 } 

             } 

         } 

     } 

     if(Dist[E]==INF) 

         return 0; 

     return 1; 

 } 

 int EK(int S,int E) 

 { 

     int u; 

     int sum=0; 

     int temp; 



     while(spfa(S,E)) 

     { 

        // printf("88888\n"); 

         sum+=Dist[E]; 

         temp=INF; 

         u=E; 

         while(u!=S) 

          { 

              if(temp>edge[prev[u]].c) 

                 temp=edge[prev[u]].c; 

              u=edge[prev[u]].u; 

          } 

          flow+=temp; 

          u=E; 

         while(u!=S) 

         { 

             edge[prev[u]].c-=temp; 

             edge[prev[u]^1].c+=temp; 

            u=edge[prev[u]].u; 

         } 

     } 

     return sum; 

 } 

 int main() 

 { 

     int n,m; 

     int i; 

     int x,y,z; 

     while(scanf("%d%d",&n,&m)!=EOF) 

     { 

         ep=0; 

         memset(head,-1,sizeof(head)); 

         flow=0; 

         for(i=1;i<=m;i++) 

         { 

             scanf("%d%d%d",&x,&y,&z); 

             Add(x,n+y,z,1); 

         } 

         for(i=1;i<=n;i++) 

         { 

             Add(0,i,0,1); 

             Add(n+i,2*n+1,0,1); 

         } 

         int ans=EK(0,2*n+1); 

         if(flow==n) 

             printf("%d\n",ans); 

         else 

             printf("-1\n"); 

     } 

     return 0; 

 }