https://www.luogu.com.cn/problem/P4174
见https://wenku.baidu.com/view/87ecda38376baf1ffc4fad25.html第24-28页，有Maxflow(n,n+m)版的模型。
1 #include<cstdio>
2 #include<cstring>
3 #include<cstdlib>
4 #include<algorithm>
5 using namespace std;
6 #define LL long long
7
8 int n,m;
9 #define maxn 5011
10 #define maxm 50011*4+maxn*4
11 struct NetEdge{int to,next,cap,flow;};
12 struct Net
13 {
14 int n,le,s,t,first[maxn],dis[maxn],cur[maxn],que[maxn],head,tail; NetEdge edge[maxm];
15 void clear(int N) {n=N; le=2; memset(first,0,sizeof(first));}
16 void in(int x,int y,int c) {NetEdge &e=edge[le]; e.to=y; e.cap=c; e.flow=0; e.next=first[x]; first[x]=le++;}
17 void insert(int x,int y,int c) {in(x,y,c); in(y,x,0);}
18 bool bfs()
19 {
20 memset(dis,0,sizeof(dis));
21 head=0; tail=1; que[0]=s; dis[s]=1;
22 while (head!=tail)
23 {
24 int x=que[head++];
25 for (int i=first[x];i;i=edge[i].next)
26 {
27 NetEdge &e=edge[i]; if (dis[e.to] || e.cap==e.flow) continue;
28 dis[e.to]=dis[x]+1; que[tail++]=e.to;
29 }
30 }
31 return dis[t]>0;
32 }
33 LL dfs(int x,int a)
34 {
35 if (x==t || !a) return (LL)a;
36 LL flow=0,f;
37 for (int &i=cur[x];i;i=edge[i].next)
38 {
39 NetEdge &e=edge[i];
40 if (dis[e.to]==dis[x]+1 && (f=dfs(e.to,min(a,e.cap-e.flow)))>0)
41 {
42 e.flow+=f;
43 flow+=f;
44 edge[i^1].flow-=f;
45 a-=f;
46 if (!a) break;
47 }
48 }
49 return flow;
50 }
51 LL Dinic(int S,int T)
52 {
53 s=S; t=T;
54 LL flow=0;
55 while (bfs())
56 {
57 for (int i=1;i<=n;i++) cur[i]=first[i];
58 flow+=dfs(s,0x3f3f3f3f);
59 }
60 return flow;
61 }
62 }g;
63
64 int p[maxn],du[maxn];
65 int main()
66 {
67 scanf("%d%d",&n,&m);
68 for (int i=1;i<=n;i++) scanf("%d",&p[i]);
69 int U=0;
70 g.clear(n+2);
71 for (int i=1,x,y,v;i<=m;i++)
72 {
73 scanf("%d%d%d",&x,&y,&v);
74 g.insert(x,y,v);
75 g.insert(y,x,v);
76 U+=v;
77 du[x]+=v; du[y]+=v;
78 }
79 for (int i=1;i<=n;i++) g.insert(n+1,i,U),g.insert(i,n+2,U+2*p[i]-du[i]);
80 printf("%lld\n",(1ll*U*n-g.Dinic(n+1,n+2))>>1);
81 return 0;
82 }
来源：https://www.cnblogs.com/Blue233333/p/12262579.html