【模板】有源汇有上下界最大流

#include <bits/stdc++.h>
using namespace std;

const int Maxn=205;
const int Maxm=10005;
const int inf=1e9;
int n,m,size=1,s,t,tot,ans,S,T,sum;
int first[Maxn],tmp[Maxn],in[Maxn],out[Maxn],depth[Maxn];
struct shu{int to,next,len,v;};
shu edge[Maxm<<3];

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)
{
	edge[++size].next=first[x];
	first[x]=size;
	edge[size].to=y;
	edge[size].len=z;
}

inline void pre()
{
	T=n+1;
	for(int i=1;i<=n;i++)
	{
	  int num=in[i]-out[i];
	  if(num>0) build(S,i,num),build(i,S,0),sum+=num;
	  if(num<0) build(i,T,abs(num)),build(T,i,0);
	}
}

inline void delet(){for(int i=tot+1;i<=size;i++) edge[i].len=0;}

inline int mn(int x,int y){return x < y ? x : y;}

inline bool bfs(int s,int t)
{
	queue<int>q;    //建议手写
	q.push(s);
	memset(depth,0,sizeof(depth));
	depth[s]=1;
	while(!q.empty())
	{
	  int point=q.front();
	  q.pop();
	  for(int u=first[point];u;u=edge[u].next)
	  {
	  	int to=edge[u].to;
	  	if(edge[u].len && !depth[to])
	  	{
	  	  depth[to]=depth[point]+1;
	  	  q.push(to);
	  	  if(to==t) return 1;
	  	}
	  }
	}
	return 0;
}

inline int dinic(int point,int flow,int t)
{
	if(point==t) return flow;
	int sum=0;
	for(int &u=tmp[point];u&&sum<flow;u=edge[u].next)
	{
	  int to=edge[u].to;
	  if(edge[u].len && depth[to] == depth[point] + 1)
	  {
	  	int minn=dinic(to,mn(flow-sum,edge[u].len),t);
	  	if(!(flow-sum)) {depth[to]=0;break;}
	  	edge[u].len-=minn,edge[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(),low=get_int(),up=get_int();
	  in[y]+=low,out[x]+=low,build(x,y,up-low),build(y,x,0);
	}
	tot=size;
	build(t,s,inf),build(s,t,0);
	pre();
	while(bfs(S,T))
	{
	  memcpy(tmp,first,sizeof(first));
	  ans+=dinic(S,inf,T);
	}
	if(ans!=sum) {cout<<"please go home to sleep\n";return 0;}
	first[S]=first[T]=0,ans=0;
	while(bfs(s,t))
	{
	  memcpy(tmp,first,sizeof(first));
	  ans+=dinic(s,inf,t);
	}

	cout<<ans<<"\n";
	return 0;
}