洛谷P3381 （最小费用最大流模板）

记得把数组开大一点，不然就RE了。。。

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 #define int long long
 4 const int N=5e5;
 5 const int M=5e5;
 6 const int INF=0x3f3f3f3f;
 7
 8 int n,m,s,t,ans,d[N],maxflow;
 9 int tot=1,adj[N],nex[M],to[M],cap[M],cost[M];
10 bool walk[N],vis[N];
11
12 void add(int u,int v,int w,int c){
13     nex[++tot]=adj[u];
14     adj[u]=tot;
15     to[tot]=v;
16     cap[tot]=w;
17     cost[tot]=c;
18 }
19
20 bool SPFA(){
21     queue<int> q;
22     for(int i=1;i<=n;i++)
23         vis[i]=false,walk[i]=false,d[i]=INF;
24     q.push(s),d[s]=0,vis[s]=true;
25     while(!q.empty()){
26         int u=q.front();q.pop();
27         vis[u]=false;
28         for(int i=adj[u];i;i=nex[i]){
29             int v=to[i];
30             if(cap[i]>0&&d[u]+cost[i]<d[v]){
31                 d[v]=d[u]+cost[i];
32                 if(!vis[v]){
33                     vis[v]=true;
34                     q.push(v);
35                 }
36             }
37         }
38     }
39     return d[t]<INF;
40 }
41
42 int dinic(int u,int fw){
43     if(u==t){
44         ans+=fw*d[t];
45         return fw;
46     }
47     walk[u]=true;
48     int rest=fw;
49     for(int i=adj[u];i&&rest;i=nex[i]){
50         int v=to[i];
51         if(!walk[v]&&cap[i]>0&&d[u]+cost[i]==d[v]){
52             int k=dinic(v,min(cap[i],rest));
53             if(k){
54                 cap[i]-=k;cap[i^1]+=k;
55                 rest-=k;
56             }
57         }
58     }
59     return fw-rest;
60 }
61
62 void solve(){
63     maxflow=ans=0;
64     while(SPFA()) maxflow+=dinic(s,INF);
65 }
66
67 signed main(){
68     cin>>n>>m>>s>>t;
69     for(int i=1;i<=m;i++){
70         int u,v,w,c;
71         cin>>u>>v>>w>>c;
72         add(u,v,w,c);
73         add(v,u,0,-c);
74     }
75     solve();
76     cout<<maxflow<<" "<<ans;
77     return 0;
78 }