pku 2987 Firing

 http://poj.org/problem?id=2987

最小閉合權迴路，詳見周伯濤的論文

#include<stdio.h>
#include<string.h>
const __int64 inf=0x3f3f3f3f3f3f3f3f;
#define N 5005
#define E 155000
int num,e,head[N];
int dep[N],que[N],cur[N];
struct node
{
	int x,y;
	int nxt;
	__int64 c;
}edge[E];
void addedge(int u,int v,__int64 c)
{
	edge[e].x=u;
	edge[e].y=v;
	edge[e].nxt=head[u];
	edge[e].c=c;
	head[u]=e++;

	edge[e].x=v;
	edge[e].y=u;
	edge[e].nxt=head[v];
	edge[e].c=0;
	head[v]=e++;
}

__int64 maxflow(int s,int t)
{
	int i,j,k,front,rear,top;
	__int64 res=0,min;
	while(1)
	{
		memset(dep,-1,sizeof(dep));
		front=0;
		rear=0;
		que[rear++]=s;
		dep[s]=0;
		while(front!=rear)
		{
			i=que[front++];
			for(j=head[i];j!=-1;j=edge[j].nxt)
				if(edge[j].c&&dep[edge[j].y]==-1)
				{
					dep[edge[j].y]=dep[i]+1;
					que[rear++]=edge[j].y;
				
				}
		}
		if(dep[t]==-1)
			break;
		memcpy(cur,head,sizeof(head)); 
		for(i=s,top=0;;)
		{
			if(i==t)
			{
				min=inf;
				for(k=0;k<top;k++)
					if(min>edge[que[k]].c)
					{
						min=edge[que[k]].c;
						front=k;
					}
				for(k=0;k<top;k++)
				{
					edge[que[k]].c-=min;
					edge[que[k]^1].c+=min;
				}
				res+=min;
				i=edge[que[top=front]].x;
				
			}
			for(j=cur[i];cur[i]!=-1;j=cur[i]=edge[cur[i]].nxt)
				if(dep[edge[j].y]==dep[i]+1&&edge[j].c)
					break;
			if(cur[i]!=-1)
			{
				que[top++]=cur[i];
				i=edge[cur[i]].y;
			}
			else
			{
				if(top==0)
					break;
				dep[i]=-1;
				i=edge[que[--top]].x;
			}
		}
	}
	return res;
}
char vis[N];
void dfs(int u)
{
	int i;
	vis[u]=1;num++;
	for(i=head[u];i!=-1;i=edge[i].nxt)
		if(edge[i].c>0&&vis[edge[i].y]==0)
			dfs(edge[i].y);
}
int main()
{
	int n,m,i,u,v;
	while(scanf("%d%d",&n,&m)!=EOF)
	{
		e=0;memset(head,-1,sizeof(head));
		__int64 sum=0,c;
		for(i=1;i<=n;i++)
		{
			scanf("%I64d",&c);
			if(c>0)
			{
				sum+=c;
				addedge(0,i,c);
			}
			else
				addedge(i,n+1,-c);
		}
		for(i=0;i<m;i++)
		{
			scanf("%d%d",&u,&v);
			addedge(u,v,inf);
		}
		__int64 ans=maxflow(0,n+1);
		memset(vis,0,sizeof(vis));
		num=-1;dfs(0);
		printf("%d %I64d\n",num,sum-ans);
	}
	return 0;
}