POJ 1523 割点

//翻译见图论书390页

 

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
using namespace std;

#define MIN(a,b) ((a)<(b)?(a):(b))

int mp1[1005];
int mp2[1005];
int g[1005][1005];
int n;
int low[1005];
int visit[1005];
int cnt;

struct solve
{
	int a;
	int b;
};
bool cmp(solve s1,solve s2)
{
	return mp2[s1.a]<mp2[s2.a];
}
solve s[1000];
int solcnt;

void dfs(int v)
{
	int res=0;
	low[v]=visit[v]=cnt++;
	for(int i=1;i<=n;i++)
	{
		if(g[v][i])
		{
			if(visit[i]==0)
			{
				dfs(i);
				if(low[i]>=visit[v])
				{
					res++;
				}
				else
				{
					low[v]=MIN(low[i],low[v]);
				}
			}
			else
			{
				low[v]=MIN(low[v],visit[i]);
			}
		}
	}
	if(res>0)
	{
		s[solcnt].a=v;
		s[solcnt].b=res+1;
		solcnt++;
	}
}

void spf()
{
	cnt=1;
	memset(visit,0,sizeof(visit));
	visit[1]=low[1]=cnt++;
	int r=0;
	for(int i=2;i<=n;i++)
	{
		if(g[1][i]&&visit[i]==0)
		{
			r++;
			dfs(i);
		}
	}
	if(r>1)
	{
		s[solcnt].a=1;
		s[solcnt].b=r;
		solcnt++;
	}
	sort(s,s+solcnt,cmp);
}

int main()
{
	int a,b=0;
	memset(g,0,sizeof(g));
	int cse=1;
	while(scanf("%d",&a))
	{
		if(a==0)
		{
			if(b==0)
			{
				break;
			}
			else
			{
				solcnt=0;
				spf();
				b=0;
				n=0;
				memset(g,0,sizeof(g));
				printf("Network #%d\n",cse++);
				if(solcnt==0)
				{
					printf("  No SPF nodes\n");
				}
				for(int i=0;i<solcnt;i++)
				{
					printf("  SPF node %d leaves %d subnets\n",mp2[s[i].a],s[i].b);
				}
				printf("\n");
				memset(mp1,0,sizeof(mp2));
				memset(mp2,0,sizeof(mp2));
				continue;
			}
		}
		scanf("%d",&b);
		if(mp1[a]==0)
		{
			mp1[a]=++n;
			mp2[n]=a;
		}
		if(mp1[b]==0)
		{
			mp1[b]=++n;
			mp2[n]=b;
		}
		g[mp1[a]][mp1[b]]=g[mp1[b]][mp1[a]]=1;
	}
	return 0;
}