解题：HNOI 2012 永无乡

题面

并查集维护连通性，然后暴力启发式合并就完了，记得合并时边DFS边清空数组

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;
 const int N=;
 int val[N],siz[N],rnk[N],son[N][];
 int aset[N],volu[N],root[N];
 int n,m,x,y,t1,t2,tot;
 char rd[];
 int finda(int x)
 {
     return x==aset[x]?x:aset[x]=finda(aset[x]);
 }
 void Pushup(int nde)
 {
     siz[nde]=siz[son[nde][]]+siz[son[nde][]]+;
 }
 int Create()
 {
     siz[++tot]=;
     rnk[tot]=rand();
     return tot;
 }
 int Merge(int x,int y)
 {
     if(!x||!y)
         return x+y;
     else if(rnk[x]<=rnk[y])
     {
         son[x][]=Merge(son[x][],y);
         Pushup(x); return x;
     }
     else
     {
         son[y][]=Merge(x,son[y][]);
         Pushup(y); return y;
     }
 }
 void Split(int nde,int &x,int &y,int tsk)
 {
     if(!nde) x=y=;
     else
     {
         if(val[nde]<=tsk)
             x=nde,Split(son[nde][],son[nde][],y,tsk);
         else
             y=nde,Split(son[nde][],x,son[nde][],tsk);
         Pushup(nde);
     }
 }
 int Query(int nde,int tsk)
 {
     if(tsk<=siz[son[nde][]]) return Query(son[nde][],tsk);
     else if(tsk==siz[son[nde][]]+) return nde;
     else return Query(son[nde][],tsk-siz[son[nde][]]-);
 }
 void Insert(int &nde,int tsk)
 {
     Split(nde,x,y,val[tsk]);
     nde=Merge(Merge(x,tsk),y);
 }
 void DFS(int &gal,int nde)
 {
     if(son[nde][]) DFS(gal,son[nde][]);
     if(son[nde][]) DFS(gal,son[nde][]);
     son[nde][]=son[nde][]=; Insert(gal,nde);
 }
 void Unite(int x,int y)
 {
     int f1=finda(x),f2=finda(y);
     if(volu[f1]<volu[f2]) swap(f1,f2);
     volu[f1]+=volu[f2],aset[f2]=f1;
     DFS(root[f1],root[f2]);
 }
 int main ()
 {
     srand();
     scanf("%d%d",&n,&m);
     for(int i=;i<=n;i++)
     {
         scanf("%d",&val[i]);
         root[i]=Create();
         aset[i]=i,volu[i]=;
     }
     while(m--)
         scanf("%d%d",&t1,&t2),Unite(t1,t2);
     scanf("%d",&m);
     while(m--)
     {
         scanf("%s%d%d",rd,&t1,&t2);
         if(rd[]=='B')
             scanf("%d%d",&t1,&t2),Unite(t1,t2);
         else
         {
             int ans=Query(root[finda(t1)],t2);
             ans?printf("%d\n",ans):printf("-1\n");
         }
     }
     return ;
 }