poj2014 不带修改区间第k大树

主席树 又称函数式线段树，又称可持久化线段树……缺点是内存有点儿大……

 1 type node1=record

 2      l,r,sum:longint;

 3      end;

 4      node2=record

 5      x,idx:longint;

 6      end;

 7 var q,i,j,k,tot,n,m:longint;

 8     a:array[0..500000] of node2;

 9     rank,root:array[0..500000] of longint;

10     t:array[0..5000000] of node1;

11 procedure qsort(h,l:longint);

12  var i,j,m:longint;

13      temp:node2;

14  begin

15  i:=h;j:=l;m:=a[(i+j)>>1].x;

16  repeat

17   while a[i].x<m do inc(i);

18   while a[j].x>m do dec(j);

19   if i<=j then

20    begin

21    temp:=a[i];a[i]:=a[j];a[j]:=temp;

22    inc(i);dec(j);

23    end;

24  until i>j;

25  if i<l then qsort(i,l);

26  if j>h then qsort(h,j);

27  end;

28 procedure insert(var x:longint;num,l,r:longint);

29  var mid:longint;

30  begin

31  t[tot]:=t[x];

32  x:=tot;

33  inc(tot);

34  inc(t[x].sum);

35  if l=r then exit;

36  mid:=(l+r)>>1;

37  if num<=mid then insert(t[x].l,num,l,mid)

38  else insert(t[x].r,num,mid+1,r);

39  end;

40 function query(i,j,k,l,r:longint):longint;

41  var mid,tmp:longint;

42  begin

43  if l=r then exit(l);

44  tmp:=t[t[j].l].sum-t[t[i].l].sum;

45  mid:=(l+r)>>1;

46  if k<=tmp then exit(query(t[i].l,t[j].l,k,l,mid))

47  else exit(query(t[i].r,t[j].r,k-tmp,mid+1,r));

48  end;

49 procedure main;

50  begin

51  t[0].l:=0;t[0].r:=0;t[0].sum:=0;root[0]:=0;

52  readln(n,m);

53  for i:=1 to n do begin read(a[i].x);a[i].idx:=i;end;

54  qsort(1,n);

55  tot:=1;

56  for i:=1 to n do rank[a[i].idx]:=i;

57  for i:=1 to n do

58   begin

59   root[i]:=root[i-1];

60   insert(root[i],rank[i],1,n);

61   end;

62  for q:=1 to m do

63   begin

64   readln(i,j,k);

65   writeln(a[query(root[i-1],root[j],k,1,n)].x);

66   end;

67  end;

68 begin

69  main;

70 end.       

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