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