LOJ [#115. 无源汇有上下界可行流](https://loj.ac/problem/115)

#115. 无源汇有上下界可行流

先扔个板子，上下界的东西一点点搞，写在奇怪的合集里面

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Code:

#include <cstdio>
#include <cstring>
#include <algorithm>
const int N=210;
const int M=3e4;
const int inf=0x3f3f3f3f;
int head[N],to[M],Next[M],edge[M],cnt=1;
void add(int u,int v,int w)
{
	to[++cnt]=v,edge[cnt]=w,Next[cnt]=head[u],head[u]=cnt;
	to[++cnt]=u,edge[cnt]=0,Next[cnt]=head[v],head[v]=cnt;
}
int n,m,ss,tt,ans[M],d[N],dep[N],q[N],l,r,sum;
int bfs()
{
	memset(dep,0,sizeof dep);
	dep[q[l=r=1]=ss]=1;
	while(l<=r)
	{
		int now=q[l++];
		for(int v,i=head[now];i;i=Next[i])
			if(edge[i]&&!dep[v=to[i]])
			{
				dep[v]=dep[now]+1;
				if((q[++r]=v)==tt) return true;
			}
	}
	return false;
}
int dfs(int now,int flow)
{
	if(now==tt) return flow;
	int res=flow,bee;
	for(int v,i=head[now];i&&res;i=Next[i])
		if(edge[i]&&dep[v=to[i]]==dep[now]+1)
		{
			bee=dfs(v,std::min(res,edge[i]));
			if(!bee) {dep[v]=0;continue;}
			res-=bee,edge[i]-=bee,edge[i^1]+=bee;
		}
	return flow-res;
}
int Dinic()
{
	int flow,maxflow=0;
	while(bfs())
        while(flow=dfs(ss,inf))
            maxflow+=flow;
	return maxflow;
}
int main()
{
	scanf("%d%d",&n,&m);
	for(int s,t,l,u,i=1;i<=m;i++)
	{
		scanf("%d%d%d%d",&s,&t,&l,&u);
		ans[i]=l;
		add(s,t,u-l);
		d[s]-=l,d[t]+=l;
	}
	ss=n+1,tt=ss+1;
	for(int i=1;i<=n;i++)
	{
		if(d[i]>0) add(ss,i,d[i]),sum+=d[i];
		else if(d[i]<0) add(i,tt,-d[i]);
	}
	int flow=Dinic();
	if(flow!=sum) return puts("NO"),0;
	puts("YES");
	for(int i=2;i<=m<<1;i+=2) printf("%d\n",ans[i>>1]+edge[i^1]);
	return 0;
}

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2019.2.17