【网络流】最大流之Dinic(模板)

#include <bits/stdc++.h>
using namespace std;
const int Max=50005;
const int inf=1e9+7;
int n,m,s,t,size=1;
long long ans;
int first[Max],depth[Max];
struct shu{int to,len,next;};
shu bian[Max*2];
int temp[Max]; 
inline int get_int()
{
   int x=0,f=1;
   char  c;
   for(c=getchar();(!isdigit(c))&&(c!='-');c=getchar());
   if(c=='-') {f=-1;c=getchar();}
   for(;isdigit(c);c=getchar()) x=(x<<3)+(x<<1)+c-'0';
   return x*f;
}
inline void build(int x,int y,int z)
{
   bian[++size].next=first[x];
   first[x]=size;
   bian[size].to=y;
   bian[size].len=z;
}
inline int bfs()
{
   memset(depth,0,sizeof(depth));
   queue<int>q;
   q.push(s);
   depth[s]=1;
   while(!q.empty())
   {
   	 int point=q.front();
   	 q.pop();
   	 for(register int u=first[point];u;u=bian[u].next)
   	   if(bian[u].len&&!depth[bian[u].to])
   	   {
   	   	 depth[bian[u].to]=depth[point]+1;
   	   	 q.push(bian[u].to);
   	   	 if(bian[u].to==t) return 1;
   	   }
   }
   return 0;
}

inline int dinic(int point,int flow)
{
   int sum=0;
   if(point==t) return flow;
   for(register int &u=temp[point];u&&sum<flow;u=bian[u].next)
     if(bian[u].len&&depth[bian[u].to]==depth[point]+1)
     {
       int minn=dinic(bian[u].to,min(flow-sum,bian[u].len));
       if(!(flow-sum)){depth[bian[u].to]=0;break;}
       bian[u].len-=minn;
       bian[u^1].len+=minn;
       sum+=minn;
     }
   return sum; 
}

int main()
{
   n=get_int();
   m=get_int();
   s=get_int();
   t=get_int();
   for(int i=1;i<=m;i++)
   {
   	 int x=get_int(),y=get_int(),z=get_int();
   	 build(x,y,z);
   	 build(y,x,0);
   }
    while(bfs()) {
   		memcpy(temp, first, sizeof(first));
	   	ans+=dinic(s,inf);
   	}
   cout<<ans<<"\n";
   return 0;
}