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最大流EK：

 1 #include <vector>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <algorithm>
 5 #define N1 210
 6 #define M1 1010
 7 #define ll long long
 8 #define dd double
 9 #define inf 0x3f3f3f3f
10 using namespace std;
11 
12 int gint()
13 {
14     int ret=0,fh=1;char c=getchar();
15     while(c<'0'||c>'9'){if(c=='-')fh=-1;c=getchar();}
16     while(c>='0'&&c<='9'){ret=ret*10+c-'0';c=getchar();}
17     return ret*fh;
18 }
19 
20 struct Edge{
21 int head[N1],to[M1<<1],nxt[M1<<1],val[M1<<1],cte;
22 void ae(int u,int v,int w)
23 {
24     cte++; to[cte]=v; val[cte]=w;
25     nxt[cte]=head[u]; head[u]=cte;
26 }
27 }e;
28 
29 int que[N1],hd,tl;
30 int flow[N1],id[N1];
31 
32 int bfs(int S,int T)
33 {
34     int x,j,v;
35     memset(flow,0,sizeof(flow));
36     memset(id,0,sizeof(id));
37     hd=1,tl=0; que[++tl]=S; flow[S]=inf;
38     while(hd<=tl)
39     {
40         x=que[hd++];
41         for(j=e.head[x];j;j=e.nxt[j])
42         {
43             v=e.to[j]; 
44             if(id[v]||e.val[j]==0) continue;
45             flow[v]=min(flow[x],e.val[j]);
46             id[v]=j; que[++tl]=v;
47         }
48     }
49     if(!flow[T]) return -1;
50     else return flow[T];
51 }
52 
53 int EK(int S,int T)
54 {
55     int x,mxflow=0,tmp;
56     while(1)
57     {
58         tmp=bfs(S,T); 
59         if(tmp==-1) return mxflow;
60         for(x=T;x!=S;x=e.to[id[x]^1])
61         {
62             e.val[id[x]]-=tmp;
63             e.val[id[x]^1]+=tmp;
64         }
65         mxflow+=tmp;
66     }
67 }
68 
69 int n,m,S,T;
70 
71 int main()
72 {
73     scanf("%d%d%d%d",&n,&m,&S,&T);
74     int i,j,k,x,y,z; e.cte=1;
75     for(i=1;i<=m;i++){ x=gint(); y=gint(); z=gint(); e.ae(x,y,z); e.ae(y,x,0); }
76     printf("%d\n",EK(S,T));
77     return 0;
78 }

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