网络流EK算法（模板）

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代码

#include<cstdio>#include<iostream>#include<cstring>#include<cmath>#include<queue>using namespace std;const int maxx=1001;int n,m,s,t,flow=0;int c[maxx][maxx],f[maxx][maxx],a[maxx],pre[maxx];int bfs(){queue<int> q;while(1){memset(a,0,sizeof(a));        q.push(s);    a[s]=1e9;    while(!q.empty()){        int u=q.front();q.pop();for(int v=1;v<=n;++v)if(!a[v] && f[u][v]<c[u][v]){pre[v]=u;q.push(v);a[v]=min(a[u],c[u][v]-f[u][v]);}}if(!a[t])break;for(int i=t;i!=s;i=pre[i]){f[pre[i]][i]+=a[t];f[i][pre[i]]-=a[t];}flow+=a[t];}return flow;}int read(){char x;while((x=getchar())<'0' || x>'9');int u=x-'0';while((x=getchar())>='0' && x<='9')u=u*10+x-'0';return u;}int main(){#ifndef ONLINE_JUDGEfreopen("input.in","r",stdin);freopen("output.out","w",stdout);#endifint i,j,k;n=read();m=read();s=read();t=read();while(m--){i=read();j=read();k=read();c[i][j]=k;}printf("%d",bfs());return 0;}

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