POJ 1144 Network 无向图求割点

来源：http://poj.org/problem?id=1144

题意：就是给你一些点，某些点之间有边。求有多少个点是割点。

思路：模板题目了，直接用无向图求个点模板就可以ac。需要注意的是输入，输入有点麻烦。以换行结尾可以写成while(getchar() != '\n')，其他没什么难度了。无向图求割点的问题可以参考http://blog.csdn.net/wmn_wmn/article/details/7893157

代码：

#include <iostream>#include <cstdio>#include <string.h>#include <vector>using namespace std;#define CLR(arr,val) memset(arr,val,sizeof(arr))const int N = 110;int low[N],dfn[N],vis[N],numblock[N];vector<int> vv[N];int numcnt,timeorder,numpoint,numson;void init(){CLR(low,0);CLR(dfn,0);CLR(vis,0);CLR(vv,0);CLR(numblock,0);numson = 0;numcnt = 0;timeorder = 0;}int min(int a,int b){return a < b ? a : b;}void dfs(int x){timeorder++;low[x] = dfn[x] = timeorder;vis[x] = 1;for(int i = 0; i < vv[x].size(); ++i){   int y = vv[x][i];   if(!vis[y]){     dfs(y); low[x] = min(low[x],low[y]); if(low[y] >= dfn[x] && x != 1){   numblock[x]++; } else if(x == 1) numson++;   }   else   low[x] = min(low[x],dfn[y]);}}int main(){//freopen("1.txt","r",stdin);while(scanf("%d",&numpoint) && numpoint){init();   int x,y;   char ch;   while(scanf("%d",&x) && x){   while(getchar() != '\n'){     scanf("%d",&y); vv[x].push_back(y); vv[y].push_back(x);   }   }       dfs(1);   for(int i = 1; i <= numpoint; ++i)   if(numblock[i])   numcnt++;   if(numson > 1)   numcnt++;   printf("%d\n",numcnt);}return 0;}