TOKI OSN Open Contest 2018 (English)


  • TOKI OSN Open Contest 2018 is an open competition mirroring the National Science Olympiad in Informatics 2018 in Indonesia (OSN Informatika 2018 in Bahasa Indonesia).
  • OSN Informatika is a national olympiad in informatics for high school students. It is the one of the stages required for Indonesian students to represent Indonesia in IOI (International Olympiad in Informatics)
  • The problemset is the same as the problemset in OSN Informatika 2018, and will be given in Bahasa Indonesia and English.
  • The contest will be held on TLX (TOKI Online Judge) (you may need to register for a TLX account if you do not have one already).
  • If you have any questions please contact

Rules Overview

  • There will be one trial session and 2 (two) competition days.
  • There will be 3 (three) problems on each day to be solved in 5 (five) hours.
  • Each contestant may submit up to 50 solutions for each problem.
  • The supported programming languages are C, C++, and Pascal.
  • During the competition, each contestant can only see their own scores.

Schedule and Technical Details

  • The contests will be held at the following time ranges:
  • Day 0: 2 July 2018 08:35 - 23:05 UTC (trial session)
  • Day 1: 3 July 2018 02:35 - 23:05 UTC
  • Day 2: 4 July 2018 02:35 - 23:05 UTC

  • Each contestant can select any 5-hour window within the time range to do the contest for each competition day.
  • All three contests are now available on TLX. Please register in those contests.
  • Each contestant may start the contest any time within the time range, by clicking the timer button.
  • There will be no additional time given if a contestant starts the contest in less than 5 hours before the contest ends.
  • The open contest doesn’t support clarifications, but all important announcements from the original contest will be broadcast as well.

Problems Types

  • There are 3 possible problem types.

  • Batch problems:
    • The most common problem type.
    • Given input, contestants write a program that reads input and writes output satisfying the problem description.
    • The program must run within the given time and memory limits.
  • Interactive problems:
    • Contestants write a program that interacts with judge’s program.
    • Judge’s program writes to stdout and is given as the input for contestant’s program.
    • Contestant’s program writes to stdout and is given as the input for judge’s program.
    • The intreaction continues until a given goal is reached.
    • Contestant’s program must output answer within the given time and memory limits.
  • Output-only problems:
    • Contestants are be given a set of input test cases.
    • Contestants submit output for each input test case.
    • Contestants do not have to write a program; the outputs may be solved manually.


  • There are two types of scoring: standard and creative.
  • Creative problems will be stated explicitly in problem description.

  • Standard scoring:
    • For batch and interactive problems:
      • A problem consists of multiple subtasks with various points.
      • A subtask consists of multiple test cases.
      • A submission gets a subtask’s points if it solves all of its test cases.
      • A problem may have open subtasks where the test cases are given to contestants.
    • For output-only problems:
      • A problem consists of multiple test cases with various points.
      • A submission gets the test case’s points if it produces the correct output.
  • Creative scoring:
    • The scoring formula will vary for each problem and will be explicitly stated in problem description.

Grading System

  • Source code limit for each submission is 300 KB.
  • For each test case, the grader will output one of:
    • AC (Accepted): program solved the problem within the given time and memory limits.
    • WA (Wrong Answer): program stopped within given time and memory limits, but produced the wrong output.
    • RTE (Runtime Error): program crashed or exceedeed the memory limit.
    • TLE (Time Limit Exceeded): program exceeded the time limit.
    • Skipped: test case is not graded because there was a test case in the same subtask that was not solved.