http://poj.org/problem?
id=1330
给一个有根树，一个查询节点(u,v)的近期公共祖先
836K 16MS
#include<iostream> #include<cstring> #include<cstdio> #include<algorithm> #include<vector> #include<string> #include<set> #include<map> const int maxn=10005; using namespace std; int n,m;//结点数，查询数 int f[maxn];//并查集 bool vis[maxn];//訪问标记 int ancestor[maxn];//祖先 int answer[2];//存储最后的查询结果 int in[maxn];//入度 vector<int> que[maxn]; struct Edge{ int to; int next; }edge[maxn<<1];int head[maxn],tot; void addedge(int u,int v){ edge[tot].to=v; edge[tot].next=head[u]; head[u]=tot++; } void Init(){ tot=0; memset(in,0,sizeof(in)); memset(f,-1,sizeof(f)); memset(head,-1,sizeof(head)); memset(vis,false,sizeof(vis)); memset(ancestor,0,sizeof(ancestor)); for(int i=1;i<=n;++i){ que[i].clear(); } } int find(int x){ return f[x]==-1 ?x:f[x]=find(f[x]); } void Union(int u,int v){ int t1=find(u); int t2=find(v); if(t1!=t2) f[t2]=t1; } void LCA(int u){ ancestor[u]=u; for(int i=head[u];i!=-1;i=edge[i].next){ int v=edge[i].to; if(vis[v]) continue; LCA(v); Union(u,v); ancestor[find(v)]=u;//可省略 } vis[u]=true; int sz=que[u].size(); for(int i=0;i<sz;++i){ int v=que[u][i]; if(vis[v]){ printf("%d\n",ancestor[find(v)]);//可替换find(v) } } } int main() { //freopen("in.txt","r",stdin); int T,u,v,w; cin>>T; while(T--){ scanf("%d",&n); Init(); for(int i=0;i<n-1;++i){ scanf("%d%d",&u,&v); if(u!=v){ addedge(u,v); in[v]++; } } scanf("%d%d",&u,&v); que[u].push_back(v); que[v].push_back(u); for(int i=1;i<=n;++i){ if(in[i]==0){ LCA(i); break; } } } return 0; }
转载于:https://www.cnblogs.com/bhlsheji/p/5344559.html
