COSCON 2025 Problems

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Welcome! There are 12 problems worth a total of 212 points. Each problem will require either submission of your solution source code to Codeforces, or submission of the files/text comprising your solution to a Google Form. If you have any questions about any problems or the competition in general, please direct them to the appropriate channel in the COSCON 2025 Discord server.

Important Information for Codeforces Problems

Each team should submit to problems under ONE CODEFORCES ACCOUNT.
Problems marked [Codeforces] can be found at this link. In particular, follow these instructions:
  1. Create a Codeforces account (if you don't have one already)
  2. Fill out this form (so we can collect your handles)
  3. Join the group using the link above (see the "Membership management" panel on right)
  4. Enter the COSCON Fall 2025 contest.
  5. Submit your solution to the appropriate problem (see navbar).
Codeforces problem will require you to take input from standard input. If you are not familiar with this, here is an example of how to read input in Java.
If you don't have an environment to run Java/Python/etc. on your device, you can try using an online compiler such as Programiz or JDoodle.
If you need more help with this, feel free to come see us in office hours (Friend 108).

Problem 1: An Encryption Dilemma [5 points]

Tags: Programming

Problem Statement Codeforces Submission

Problem 2: Cell Capture [10 points]

Tags: Programming

Problem Statement Codeforces Submission

Problem 3: Life [20 points]

Tags: Programming

Problem Statement Codeforces Submission (1) Codeforces Submission (2)

Problem 4: Virtual Memory [18 points]

Tags: Systems

Problem Statement seq3.txt Submission

Problem 5: Login Vault [26 points]

Tags: Capture The Flag

In this problem, you will need to interact with our server and find a way to retrieve the flag.

For Login Vault 2, bypassing authentication is not enough. You need to find the admin password.

Note: the server has now been disabled. Static files can be found below.

Problem Statement Archive Submission

Problem 6: Tetris Melons [20 points]

Tags: Optimization

Problem Statement Starter Code File Submission

Problem 7: PSet Groups [18 points]

Tags: Theory

Problem Statement File Submission

Problem 8: Fall Foliage [20 points]

Tags: Theory

Problem Statement File Submission

Problem 9: Let It Glow! [20 points]

Tags: Optimization

Problem Statement Starter Code Submission

Problem 10: Caching [20 points]

Tags: Systems

Problem Statement alloc.c alloc.h cache.h grader.c starter.c (Starter Code) Sample Input (Task 1) Sample Input (Task 2) Submission

Problem A: COSCON Trading Challenge [20 points]

Tags: Trading

Live event

Slides

Problem B: Castle Invasion [15 points]

Tags: Game Theory

Check #announcements in the Discord for updates

Problem Statement