ORDERSET - Order statistic set

In this problem, you have to maintain a dynamic set of numbers which support the two fundamental operations

  • INSERT(S,x): if x is not in S, insert x into S
  • DELETE(S,x): if x is in S, delete x from S

and the two type of queries

  • K-TH(S) : return the k-th smallest element of S
  • COUNT(S,x): return the number of elements of S smaller than x


  • Line 1: Q (1 ≤ Q ≤ 200000), the number of operations
  • In the next Q lines, the first token of each line is a character I, D, K or C meaning that the corresponding operation is INSERT, DELETE, K-TH or COUNT, respectively, following by a whitespace and an integer which is the parameter for that operation.

If the parameter is a value x, it is guaranteed that 0 ≤ |x| ≤ 109. If the parameter is an index k, it is guaranteed that 1 ≤ k ≤ 109.


For each query, print the corresponding result in a single line. In particular, for the queries K-TH, if k is larger than the number of elements in S, print the word 'invalid'.


I -1
I -1
I 2
C 0
K 2
D -1
K 1
K 2


hide comments
kshubham02: 2019-04-14 13:01:17

@man_of_silence, it is 0<=|x|<=10^9.
It is different from 0<= x <= 10^9.

man_of_silence: 2019-03-01 08:28:34

isn't 0 <= x, misleading? Because in the above test cases x is negative.

nikhil2504: 2018-12-29 13:58:30

nice problem

k0walsk1: 2018-09-24 14:36:51

Policy Based Data Structures are so OP lul

badboy_1496: 2018-08-11 09:30:22

AC in one go ,,,,,use of BIT and binary search and cordinate compression!!!!

Last edit: 2018-08-11 09:31:31
luka_dzimba911: 2018-07-25 03:56:04

Can anyone explain how to get under 0.5 s i have 0.84s and have been using AVL no optimizations . Thanks in advance

kaushalag29: 2018-06-23 07:11:35

@Duc Plz check my solution #id 21882541.Getting WA after 5th test case.Is it due to getchar()?

jmr99: 2018-06-18 23:48:44

refer this.. for policy based data structures in C++


divyansh121212: 2018-06-14 23:22:42

Solved using Treaps

scube97: 2018-04-27 19:46:40

Why is the time limit so strict ? Tried everything , unordered_map,changes long long to int,but to no avail still a tle. Approach segment tree after compression.Each query in O(logn*logn)

Last edit: 2018-04-27 19:47:21

Added by:Duc
Time limit:0.300s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: ERL JS-RHINO NODEJS PERL6 VB.NET
Resource:© VNOI