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
1 #include<cstdio> 2 #include<cstring> 3 #include<algorithm> 4 using namespace std; 5 const int N=100005; 6 int val[N],siz[N],rnk[N],son[N][2]; 7 int aset[N],volu[N],root[N]; 8 int n,m,x,y,t1,t2,tot; 9 char rd[5]; 10 int finda(int x) 11 { 12 return x==aset[x]?x:aset[x]=finda(aset[x]); 13 } 14 void Pushup(int nde) 15 { 16 siz[nde]=siz[son[nde][0]]+siz[son[nde][1]]+1; 17 } 18 int Create() 19 { 20 siz[++tot]=1; 21 rnk[tot]=rand(); 22 return tot; 23 } 24 int Merge(int x,int y) 25 { 26 if(!x||!y) 27 return x+y; 28 else if(rnk[x]<=rnk[y]) 29 { 30 son[x][1]=Merge(son[x][1],y); 31 Pushup(x); return x; 32 } 33 else 34 { 35 son[y][0]=Merge(x,son[y][0]); 36 Pushup(y); return y; 37 } 38 } 39 void Split(int nde,int &x,int &y,int tsk) 40 { 41 if(!nde) x=y=0; 42 else 43 { 44 if(val[nde]<=tsk) 45 x=nde,Split(son[nde][1],son[nde][1],y,tsk); 46 else 47 y=nde,Split(son[nde][0],x,son[nde][0],tsk); 48 Pushup(nde); 49 } 50 } 51 int Query(int nde,int tsk) 52 { 53 if(tsk<=siz[son[nde][0]]) return Query(son[nde][0],tsk); 54 else if(tsk==siz[son[nde][0]]+1) return nde; 55 else return Query(son[nde][1],tsk-siz[son[nde][0]]-1); 56 } 57 void Insert(int &nde,int tsk) 58 { 59 Split(nde,x,y,val[tsk]); 60 nde=Merge(Merge(x,tsk),y); 61 } 62 void DFS(int &gal,int nde) 63 { 64 if(son[nde][0]) DFS(gal,son[nde][0]); 65 if(son[nde][1]) DFS(gal,son[nde][1]); 66 son[nde][0]=son[nde][1]=0; Insert(gal,nde); 67 } 68 void Unite(int x,int y) 69 { 70 int f1=finda(x),f2=finda(y); 71 if(volu[f1]<volu[f2]) swap(f1,f2); 72 volu[f1]+=volu[f2],aset[f2]=f1; 73 DFS(root[f1],root[f2]); 74 } 75 int main () 76 { 77 srand(20020513); 78 scanf("%d%d",&n,&m); 79 for(int i=1;i<=n;i++) 80 { 81 scanf("%d",&val[i]); 82 root[i]=Create(); 83 aset[i]=i,volu[i]=1; 84 } 85 while(m--) 86 scanf("%d%d",&t1,&t2),Unite(t1,t2); 87 scanf("%d",&m); 88 while(m--) 89 { 90 scanf("%s%d%d",rd,&t1,&t2); 91 if(rd[0]=='B') 92 scanf("%d%d",&t1,&t2),Unite(t1,t2); 93 else 94 { 95 int ans=Query(root[finda(t1)],t2); 96 ans?printf("%d ",ans):printf("-1 "); 97 } 98 } 99 return 0; 100 }