Dinic

BFS构造分层网络，DFS多路增广

 #include<iostream>
 #include<vector>
 #include<queue>
 #include<cstring>
 using namespace std;
 ;
 <<;
 struct Edge{
     int from,to,flow,cap;
 };
 struct Dinic{
     int vis[maxn],cur[maxn],d[maxn];
     vector<Edge> edges;
     vector<int> G[maxn];
     int s,t;
     void addEdge(int from,int to,int cap)
     {
         edges.push_back((Edge){,cap});
         G[);
         edges.push_back((Edge){to,,});
         G[to].push_back(edges.size()-);
     }
     int BFS()
     {
         memset(vis,,sizeof(vis));
         queue<int> Q;
         Q.push(s);
         vis[s]=;
         d[s]=;
         while(!Q.empty()){
             int x=Q.front();Q.pop();
             ;i<G[x].size();i++){
                 Edge& e=edges[G[x][i]];
                 if(!vis[e.to]&&e.cap>e.flow){
                     vis[e.to]=;
                     d[e.to]=d[x]+;
                     Q.push(e.to);
                 }
             }
         }
         return vis[t];
     }
     int DFS(int u,int a)
     {
         ) return a;
         ,f;
         for(int& i=cur[u];i<G[u].size();i++){
             Edge& e=edges[G[u][i]];
             &&(f=DFS(e.to,min(a,e.cap-e.flow)))>){
                 e.flow+=f;
                 edges[G[u][i]^].flow-=f;
                 flow+=f;
                 a-=f;
                 if(!a) break;
             }
         }
         return flow;
     }
     int MaxFlow(int ss,int tt)
     {
         ;
         s=ss,t=tt;
         while(BFS()){
             memset(cur,,sizeof(cur));
             ans+=DFS(s,inf);
         }
         return ans;
     }
 };
 Dinic solver;
 int main()
 {
     int n,m;
     cin>>n>>m;
     ;i<=m;i++){
         int from,to,cap;
         cin>>from>>to>>cap;
         solver.addEdge(from,to,cap);
     }
     cout<<solver.MaxFlow(,n);
     ;
 }