http://poj.org/problem?id=1144
1 #include<cstdio> 2 #include<cstring> 3 #include<algorithm> 4 #include<vector> 5 using namespace std; 6 7 const int mx=105; 8 vector<int>map[mx]; 9 int dfn[mx],low[mx],vs[mx],flag[mx]; 10 int dfn_cut; 11 12 void dfs(int v,int u) 13 { 14 int child=0; 15 dfn[v]=low[v]=++dfn_cut; 16 vs[v]=1; 17 for (int i=0;i<map[v].size();i++) 18 { 19 int w=map[v][i]; 20 if (!vs[w]) 21 { 22 child++; 23 dfs(w,v); 24 low[v]=min(low[v],low[w]); 25 if (child>1&&v==1) flag[v]=1; 26 if (v!=1&&low[w]>=dfn[v]) flag[v]=1; 27 } 28 else if (w!=u&&u!=-1) low[v]=min(low[v],dfn[w]); 29 } 30 } 31 32 int main() 33 { 34 int n,x,y; 35 while (~scanf("%d",&n)&&n) 36 { 37 for (int i=1;i<=n;i++) map[i].clear(); 38 while (~scanf("%d",&x)&&x) 39 { 40 char c; 41 while (c=getchar()!=' ') 42 { 43 scanf("%d",&y); 44 map[x].push_back(y); 45 map[y].push_back(x); 46 } 47 } 48 memset(low,0,sizeof(low)); 49 memset(dfn,0,sizeof(dfn)); 50 memset(vs,0,sizeof(vs)); 51 memset(flag,0,sizeof(flag)); 52 dfn_cut=0; 53 dfs(1,-1); 54 int ans=0; 55 for (int i=1;i<=n;i++) ans+=flag[i]; 56 printf("%d ",ans); 57 } 58 }
终于做了一道割点题，虽然还不太懂