学步园

#define INF 2000000000
#define typec int//type of cost
const int pN=600000,eN=3000000;
struct Edge{
	int u,v,next;
	typec w;
};
Edge edge[eN];
int en,head[pN],cur[pN],ps[pN],dep[pN];
void insert(int u,int v,typec w){
	edge[en].u=u;
	edge[en].v=v;
	edge[en].w=w;
	edge[en].next=head[u];
	head[u]=en++;
	edge[en].u=v;
	edge[en].v=u;
	edge[en].w=0;//有向为0，无向为w
	edge[en].next=head[v];
	head[v]=en++;
}
typec max_flow(int n,int s,int t){
	typec tr,res=0;
	int i,j,k,f,r,top;
	while(1){
		memset(dep,-1,n*sizeof(int));
		for(f=dep[ps[0]=s]=0,r=1;f!=r;)
			for(i=ps[f++],j=head[i];j!=-1;j=edge[j].next){
				if(edge[j].w&&-1==dep[k=edge[j].v]){
					dep[k]=dep[i]+1;
					ps[r++]=k;
					if(k==t){
						f=r;
						break;
					}
				}
			}
			if(-1==dep[t])break;
			memcpy(cur,head,n*sizeof(int));
			for(i=s,top=0;;){
				if(i==t){
					for(k=0,tr=INF;k<top;++k)
						if(edge[ps[k]].w<tr)
							tr=edge[ps[f=k]].w;
						for(k=0;k<top;++k)
							edge[ps[k]].w-=tr,edge[ps[k]^1].w+=tr;
						res+=tr;
						i=edge[ps[top=f]].u;
				}
				for(j=cur[i];cur[i]!=-1;j=cur[i]=edge[cur[i]].next)
					if(edge[j].w&&dep[i]+1==dep[edge[j].v])break;
					if(cur[i]!=-1){
						ps[top++]=cur[i];
						i=edge[cur[i]].v;
					}else{
						if(0==top)break;
						dep[i]=-1;
						i=edge[ps[--top]].u;
					}
			}
	}
	return res;
}