【BZOJ2733】永无乡（线段树，启发式合并）

题意：支持合并，求块内K小数

对于 100%的数据 n≤100000,m≤n，q≤300000

思路：对于每一个块建立一棵动态开点的线段树，暴力（启发式？）合并后二分下就行了

merge用函数的方式写因为懒得讨论x,y其中一个为0的情况，反正是把节点y并到x上

为什么这么暴力都不T？大概是因为随机数据的块的大小太平均了吧

 var t:array[..,..]of longint;
     sum:array[..]of longint;
     fa,a,root:array[..]of longint;
     n,m,x,y,k,i,j,s,cnt,p,q:longint;
     ch:string;

 function find(k:longint):longint;
 begin
  if fa[k]<>k then fa[k]:=find(fa[k]);
  exit(fa[k]);
 end;

 procedure pushup(x:longint);
 var l,r:longint;
 begin
  l:=t[x,]; r:=t[x,];
  sum[x]:=sum[l]+sum[r];
 end;

 procedure update(l,r,x:longint;var p:longint);
 var mid:longint;
 begin
  if p= then
  begin
   inc(cnt); p:=cnt;
  end;
  if l=r then
  begin
   inc(sum[p]); exit;
  end;
  mid:=(l+r)>>;
  if x<=mid then update(l,mid,x,t[p,])
   else update(mid+,r,x,t[p,]);
  pushup(p);
 end;

 function merge(x,y:longint):longint;
 var mid:longint;
 begin
  if (x=)or(y=) then exit(x+y);
  t[x,]:=merge(t[x,],t[y,]);
  t[x,]:=merge(t[x,],t[y,]);
  pushup(x);
  exit(x);
 end;

 function query(l,r,k,p:longint):longint;
 var mid,tmp:longint;
 begin
  if sum[p]<k then exit(-);
  if l=r then exit(a[l]);
  tmp:= sum[t[p,]];
  mid:=(l+r)>>;
  if tmp>=k then exit(query(l,mid,k,t[p,]))
   else exit(query(mid+,r,k-tmp,t[p,]));
 end;

 begin
  assign(input,'bzoj2733.in'); reset(input);
  assign(output,'bzoj2733.out'); rewrite(output);
  readln(n,m);
  for i:= to n do
  begin
   read(x); a[x]:=i;
   update(,n,x,root[i]);
  end;
  for i:= to n do fa[i]:=i;
  for i:= to m do
  begin
   readln(x,y);
   p:=find(x); q:=find(y);
   if p<>q then
   begin
    fa[q]:=p;
    merge(root[p],root[q]);
   end;
  end;
  readln(m);
  for i:= to m do
  begin
   readln(ch);
   s:=; x:=; y:=; k:=length(ch);
   for j:= to k do
   begin
    if ch[j]=' ' then begin inc(s); continue; end;
    if s= then x:=x*+ord(ch[j])-ord('');
    if s= then y:=y*+ord(ch[j])-ord('');
   end;
   case ch[] of
    'Q':writeln(query(,n,y,root[find(x)]));
    'B':
    begin
     p:=find(x); q:=find(y);
     if p<>q then
     begin
      fa[q]:=p; root[p]:=merge(root[p],root[q]);
     end;
    end;
   end;
  end;

  close(input);
  close(output);
 end.