Contest Formats

LCOJ supports 6 contest formats: Default, IOI, Legacy IOI, ECOO, AtCoder, and ICPC.

Default

The standard and simplest format.

Scoring:

• Score = Sum of the highest score on each problem
• Tiebreaker: Time of the last scoring submission

Note: Every submission adds to the penalty time, even submissions that do not increase your score.

Configuration: No special options.

Example:

Contestant	Problem A	Problem B	Problem C	Total score	Time
Alice	100 (10m)	80 (25m)	60 (40m)	240	40m
Bob	100 (15m)	80 (20m)	60 (35m)	240	35m

Bob wins because his time is lower.

IOI

The format of the International Olympiad in Informatics.

Scoring:

• Each problem has multiple subtasks
• Subtask score = Highest score on that subtask across all submissions
• Problem score = Sum of subtask scores
• Total score = Sum of problem scores
• No tiebreaker by default

Example:

Problem A has 2 subtasks (30 points and 70 points):

Submission	Subtask 1	Subtask 2	Total
Attempt 1	30	10	40
Attempt 2	0	70	70
Final score	30	70	100

Options:

{
  "cumtime": true
}

If cumtime: true, ties are broken by the total time of the first submission that passes each subtask.

Legacy IOI

The format of the Codechef IOI Ranklist.

Scoring:

• Score = Sum of the highest score on each problem
• No tiebreaker by default

Options:

{
  "cumtime": true
}

If cumtime: true, ties are broken by the total time of the most recent score-changing submissions.

ECOO

The format of the ECOO contest.

Scoring:

• Score = Sum of the scores of the last submission on each problem
• No tiebreaker by default

Options:

{
  "cumtime": true,
  "first_ac_bonus": 10,
  "time_bonus": 5
}

first_ac_bonus: Bonus points for getting AC on the first attempt (default 10).

time_bonus: Time-based bonus points. You earn 1 point for every time_bonus minutes remaining before the contest ends (default 5).

time_bonus example:

• A submission scores 50/100 points
• It is submitted with 23 minutes remaining
• Bonus = ⌊23/5⌋ = 4 points
• Total = 50 + 4 = 54 points

AtCoder

The AtCoder format.

Scoring:

• Score = Sum of the highest score on each problem
• Tiebreaker: Time of the last score-changing submission + penalty

Penalty:

{
  "penalty": 5
}

Penalty = Number of wrong submissions before the correct one × penalty minutes (default 5).

Example:

Problem A:

• Attempt 1 (5m): 0 points
• Attempt 2 (10m): 0 points
• Attempt 3 (15m): 100 points

Penalty = 2 × 5 = 10 minutes

Time = 15 + 10 = 25 minutes

ICPC

The ACM-ICPC format.

Scoring:

• Score = Number of problems solved (AC)
• Tiebreaker 1: Total time + penalty
• Tiebreaker 2: Time of the last score-changing submission

Penalty:

{
  "penalty": 20
}

Penalty = Number of wrong submissions before the AC submission × penalty minutes (default 20).

Example:

Problem	AC time	Wrong attempts	Penalty	Total time
A	10m	0	0	10m
B	25m	2	40m	65m
C	50m	1	20m	70m

Total: 3 problems, 145 minutes

Format comparison

Format	Score	Tiebreaker	Penalty	Best for
Default	Sum of highest scores	Last time	Every submission	Regular contests
IOI	Sum of subtask scores	None	None	Olympiads, problems with subtasks
Legacy IOI	Sum of highest scores	Optional	None	Similar to IOI
ECOO	Last submission score	Optional	Has bonuses	ECOO contests
AtCoder	Sum of highest scores	Time + penalty	Wrong submissions	AtCoder-style contests
ICPC	Problems solved (AC)	Time + penalty	Wrong submissions	ACM-ICPC

Choosing a format

Default: Best for regular contests; easy to understand.

IOI: Use when problems have clear subtasks and you want contestants to earn partial points.

ICPC: Use when you want to focus on the number of problems solved and partial points do not matter.

AtCoder: Balances score and time, with a light penalty.

ECOO: Has special features such as a first-AC bonus and a time bonus.

Configuring in the admin

1. Open the create/edit contest page
2. Select a Contest format
3. Enter a JSON config if needed (for example: {"cumtime": true, "penalty": 10})
4. Save

Example config:

{
  "cumtime": true,
  "penalty": 10,
  "first_ac_bonus": 15,
  "time_bonus": 3
}