無源匯上下界可行流模版

http://acm.sgu.ru/problem.php?contest=0&problem=194

#include<cstdio>
#include<iostream>
#include<cstring>
using namespace std;
const int maxn = 210;
const int maxm = 50000;
const int INF = 0x3ffffff;
struct Side{
	int to,next,c;
}side[maxm*2];
int node[maxn],dis[maxn],gap[maxn],start,end,cnt,top;
void add_side(int u,int v,int c){
	side[top]=(Side){v,node[u],c};node[u]=top++;
	side[top]=(Side){u,node[v],0};node[v]=top++;
}
int get_flow(int u,int flow){
	if(u==end)return flow;
	int ans=0;
	for(int i=node[u];i!=-1;i=side[i].next){
		int v=side[i].to,c=side[i].c;
		if(dis[u]>dis[v]&&c){
			int f=get_flow(v,min(flow-ans,c));
			ans+=f;
			side[i].c-=f;
			side[i^1].c+=f;
			if(ans==flow)return flow;
		}
	}
	if(!(--gap[dis[u]]))dis[start]=cnt+2;
	gap[++dis[u]]++;
	return ans;
}
int up[maxm],low[maxm],du[maxn],id[maxm];
int main(){
	int n,m;
	memset(node,-1,sizeof(node));
	scanf("%d%d",&n,&m);
	cnt=n+2;start=0;end=n+1;
	for(int i=0;i<m;i++){
		int u,v;
		scanf("%d%d%d%d",&u,&v,&low[i],&up[i]);
		du[v]+=low[i];
		du[u]-=low[i];
		add_side(u,v,up[i]-low[i]);
		id[i]=top-1;
	}
	int target=0;
	for(int i=1;i<=n;i++){
		if(du[i]>0){add_side(start,i,du[i]);target+=du[i];}
		else if(du[i]<0)add_side(i,end,-du[i]);
	}
	int ans=0;
	gap[0]=cnt;
	while(dis[start]<cnt)ans+=get_flow(start,INF);
	if(ans==target){
		printf("YES\n");
		for(int i=0;i<m;i++)printf("%d\n",low[i]+side[id[i]].c);
	}else printf("NO\n");
}