双连通分量：
//#pragma comment(linker, "/STACK:1024000000,1024000000") #include<cstdio> #include<cstring> #include<cstdlib> #include<algorithm> #include<iostream> #include<sstream> #include<cmath> #include<climits> #include<string> #include<map> #include<queue> #include<vector> #include<stack> #include<set> using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair<int,int> pii; #define pb(a) push(a) #define INF 0x1f1f1f1f #define lson idx<<1,l,mid #define rson idx<<1|1,mid+1,r #define PI 3.1415926535898 template<class T> T min(const T& a,const T& b,const T& c) { return min(min(a,b),min(a,c)); } template<class T> T max(const T& a,const T& b,const T& c) { return max(max(a,b),max(a,c)); } void debug() { #ifdef ONLINE_JUDGE #else freopen("d:\in1.txt","r",stdin); freopen("d:\out1.txt","w",stdout); #endif } int getch() { int ch; while((ch=getchar())!=EOF) { if(ch!=' '&&ch!=' ')return ch; } return EOF; } struct Edge { int u,v; }; const int maxn=50005; int pre[maxn],bccno[maxn],iscut[maxn]; int dfs_clock,bcc_cnt; vector<int> g[maxn],bcc[maxn]; stack<Edge> s; int dfs(int u,int fa) { int lowu=pre[u]=++dfs_clock; int child=0; for(int i=0;i<g[u].size();i++) { int v=g[u][i]; Edge e = (Edge){u,v}; if(!pre[v]) { s.push(e); child++; int lowv=dfs(v,u); lowu=min(lowu,lowv); if(lowv>=pre[u]) { iscut[u]=1; bcc_cnt++;bcc[bcc_cnt].clear(); while(1) { Edge x = s.top();s.pop(); if(bccno[x.u]!=bcc_cnt) { bccno[x.u]=bcc_cnt; bcc[bcc_cnt].push_back(x.u); } if(bccno[x.v]!=bcc_cnt) { bccno[x.v]=bcc_cnt; bcc[bcc_cnt].push_back(x.v); } if(x.u==u&&x.v==v)break; } } }else if(pre[v]<=pre[u]&&v!=fa) { lowu=min(lowu,pre[v]); s.push(e); } } if(child==1&&fa<0)iscut[u]=0; return lowu; } void find_bcc() { memset(bccno,0,sizeof(bccno)); memset(pre,0,sizeof(bccno)); memset(iscut,0,sizeof(iscut)); dfs_clock=bcc_cnt=0; dfs(1,-1); } int main() { int n; int ca=0; while(scanf("%d",&n)!=EOF&&n) { for(int i=1;i<=n+1;i++) g[i].clear(); for(int i=1;i<=n;i++) { int u,v; scanf("%d%d",&u,&v); g[u].push_back(v); g[v].push_back(u); } find_bcc(); // printf("test begin:----------------------------- "); // for(int i=1;i<=bcc_cnt;i++) // { // for(int j=0;j<bcc[i].size();j++) // printf("%d ",bcc[i][j]); // printf(" "); // } // printf("test end :----------------------------- "); long long ans1=0,ans2=1; for(int i=1;i<=bcc_cnt;i++) { int cut_cnt=0; for(int j=0;j<bcc[i].size();j++) { if(iscut[bcc[i][j]])cut_cnt++; } if(cut_cnt==1) { ans1++;ans2*=(long long)(bcc[i].size()-cut_cnt); } } if(bcc_cnt==1) { ans1=2; ans2=(long long)bcc[1].size()*(bcc[1].size()-1)/2; } printf("Case %d: %lld %lld ",++ca,ans1,ans2); } return 0; }
割点，两次DFS：
//#pragma comment(linker, "/STACK:1024000000,1024000000") #include<cstdio> #include<cstring> #include<cstdlib> #include<algorithm> #include<iostream> #include<sstream> #include<cmath> #include<climits> #include<string> #include<map> #include<queue> #include<vector> #include<stack> #include<set> using namespace std; typedef long long ll; typedef unsigned long long ull; typedef pair<int,int> pii; #define pb(a) push(a) #define INF 0x1f1f1f1f #define lson idx<<1,l,mid #define rson idx<<1|1,mid+1,r #define PI 3.1415926535898 template<class T> T min(const T& a,const T& b,const T& c) { return min(min(a,b),min(a,c)); } template<class T> T max(const T& a,const T& b,const T& c) { return max(max(a,b),max(a,c)); } void debug() { #ifdef ONLINE_JUDGE #else freopen("d:\in1.txt","r",stdin); freopen("d:\out1.txt","w",stdout); #endif } int getch() { int ch; while((ch=getchar())!=EOF) { if(ch!=' '&&ch!=' ')return ch; } return EOF; } struct Edge { int u,v; }; const int maxn=50005; int pre[maxn],iscut[maxn],dfs_clock; int vis[maxn]; vector<int> g[maxn]; int dfs1(int u,int fa) { int lowu=pre[u]=++dfs_clock; int child=0; for(int i=0;i<g[u].size();i++) { int v=g[u][i]; if(!pre[v]) { child++; int lowv=dfs1(v,u); lowu=min(lowu,lowv); if(lowv>=pre[u]) { iscut[u]=1; } }else if(pre[v]<pre[u]&&v!=fa) { lowu=min(lowu,pre[v]); } } if(child==1&&fa==-1) iscut[u]=0; return lowu; } void init(int n) { memset(iscut,0,sizeof(iscut)); memset(pre,0,sizeof(pre)); memset(vis,0,sizeof(vis)); dfs_clock=0; for(int i=1;i<=n+1;i++) g[i].clear(); } int read(int n) { int maxid=0; for(int i=1;i<=n;i++) { int u,v; scanf("%d%d",&u,&v); g[u].push_back(v); g[v].push_back(u); maxid=max(maxid,u,v); } return maxid; } void dfs2(int u,int &num,int &cut_cnt,int k) { num++; vis[u]=1; for(int i=0;i<g[u].size();i++) { int v=g[u][i]; if(!iscut[v]&&!vis[v]) dfs2(v,num,cut_cnt,k); else if(iscut[v]&&vis[v]!=k) { cut_cnt++; vis[v]=k; } } } int main() { int n; int ca=0; while(scanf("%d",&n)!=EOF&&n) { init(n); int m=read(n); dfs1(1,-1); long long ans1=0,ans2=1; int bcc_cnt=0; for(int i=1;i<=m;i++) { if(!iscut[i]&&!vis[i]) { int num=0,cut_cnt=0; dfs2(i,num,cut_cnt,++bcc_cnt); if(cut_cnt==1) { ans1++; ans2*=(long long)num; }else if(cut_cnt==0) { ans1=2; ans2=(long long)num*(num-1)/2; } } } printf("Case %d: %lld %lld ",++ca,ans1,ans2); } return 0; }