【POJ1144】Network
题面太长而且是英文不贴
大意：求割点
裸题
/*To The End Of The Galaxy*/ #include<cstdio> #include<cstdlib> #include<iostream> #include<cstring> #include<algorithm> #include<queue> #include<iomanip> #include<bitset> #include<stack> #include<map> #include<set> #include<cmath> #include<complex> #define debug(x) cerr<<#x<<"="<<x<<endl #define INF 0x7f7f7f7f #define llINF 0x7fffffffffffll using namespace std; typedef pair<int,int> pii; typedef long long ll; inline int init() { int now=0,ju=1;char c;bool flag=false; while(1) { c=getchar(); if(c=='-')ju=-1; else if(c>='0'&&c<='9') { now=now*10+c-'0'; flag=true; } else if(flag)return now*ju; } } inline long long llinit() { long long now=0,ju=1;char c;bool flag=false; while(1) { c=getchar(); if(c=='-')ju=-1; else if(c>='0'&&c<='9') { now=now*10+c-'0'; flag=true; } else if(flag)return now*ju; } } int cnt,n; struct edge { int from,to,val,pre; }Edge[100005]; int dfn[105],dfs_time,low[105],head[105]; bool iscut[105],vis[105]; inline void addedge(int from,int to,int val) { ++cnt; Edge[cnt]=((edge){from,to,val,head[from]}); head[from]=cnt; } inline void tarjan(int now,int fa) { int ch=0; dfn[now]=low[now]=++dfs_time; vis[now]=1; for(int j=head[now];j;j=Edge[j].pre) { if(!dfn[Edge[j].to]) { ch++; tarjan(Edge[j].to,now); low[now]=min(low[now],low[Edge[j].to]); if(low[Edge[j].to]>=dfn[now]) { iscut[now]=1; } } else if(dfn[Edge[j].to]<dfn[now]&&Edge[j].to!=fa) { low[now]=min(low[now],dfn[Edge[j].to]); } } if(!fa) { if(ch==1)iscut[now]=0; } } int main() { int n,u,v,ans; while(scanf("%d",&n),n) { cnt=0;memset(head,0,sizeof(head)); ans=0; memset(dfn,0,sizeof(dfn));memset(low,0,sizeof(low)); dfs_time=0; for(int i=1;i<=n;i++) { iscut[i]=false; vis[i]=false; } while(scanf("%d",&u),u) { while(getchar()!='\n') { scanf("%d",&v); addedge(u,v,1); addedge(v,u,1); } } for(int i=1;i<=n;i++) { if(!vis[i]) { tarjan(i,0); } } for(int i=1;i<=n;i++) { if(iscut[i]) { ans++; } } printf("%d\n",ans); } return 0; }
UPD
看起来用vis是对的而且不用vis也是对的
/*To The End Of The Galaxy*/ #include<cstdio> #include<cstdlib> #include<iostream> #include<cstring> #include<algorithm> #include<queue> #include<iomanip> #include<bitset> #include<stack> #include<map> #include<set> #include<cmath> #include<complex> #define debug(x) cerr<<#x<<"="<<x<<endl #define INF 0x7f7f7f7f #define llINF 0x7fffffffffffll using namespace std; typedef pair<int,int> pii; typedef long long ll; inline int init() { int now=0,ju=1;char c;bool flag=false; while(1) { c=getchar(); if(c=='-')ju=-1; else if(c>='0'&&c<='9') { now=now*10+c-'0'; flag=true; } else if(flag)return now*ju; } } inline long long llinit() { long long now=0,ju=1;char c;bool flag=false; while(1) { c=getchar(); if(c=='-')ju=-1; else if(c>='0'&&c<='9') { now=now*10+c-'0'; flag=true; } else if(flag)return now*ju; } } int cnt,n; struct edge { int from,to,val,pre; }Edge[100005]; int dfn[105],dfs_time,low[105],head[105]; bool iscut[105],vis[105]; inline void addedge(int from,int to,int val) { ++cnt; Edge[cnt]=((edge){from,to,val,head[from]}); head[from]=cnt; } inline void tarjan(int now,int fa) { int ch=0; dfn[now]=low[now]=++dfs_time; vis[now]=1; for(int j=head[now];j;j=Edge[j].pre) { if(!dfn[Edge[j].to]) { ch++; tarjan(Edge[j].to,now); low[now]=min(low[now],low[Edge[j].to]); if(low[Edge[j].to]>=dfn[now]) { iscut[now]=1; } } else if(vis[Edge[j].to]&&Edge[j].to!=fa) { low[now]=min(low[now],dfn[Edge[j].to]); } } if(!fa) { if(ch==1)iscut[now]=0; } } int main() { int n,u,v,ans; while(scanf("%d",&n),n) { cnt=0;memset(head,0,sizeof(head)); ans=0; memset(dfn,0,sizeof(dfn));memset(low,0,sizeof(low)); dfs_time=0; for(int i=1;i<=n;i++) { iscut[i]=false; vis[i]=false; } while(scanf("%d",&u),u) { while(getchar()!='\n') { scanf("%d",&v); addedge(u,v,1); addedge(v,u,1); } } for(int i=1;i<=n;i++) { if(!vis[i]) { tarjan(i,0); } } for(int i=1;i<=n;i++) { if(iscut[i]) { ans++; } } printf("%d\n",ans); } return 0; }
UPD2
当一张图只有两个点时 根一定会被误判为割点 判掉就好
