HKOI Online Judge ( is originally the training platform for the HKOI Training Team. Students can submit programs to improve their programming and problem solving skills. To further promote computational thinking and STEM education, the Online Judge is now open to secondary schools in Hong Kong.

Enter HKOI Online Judge

What is an Online Judge?

Online Judge is a system to perform black-box testing of programs. To solve a problem, the user will design an algorithm and implement the solution by writing a program. The program will then be compiled and tested using a number of test cases (usually hidden). For each input, the program must output the correct answer within some time and memory constraints. (e.g. in 1 second using not more than 256 MB RAM)

See a sample task with solution and test cases


Language Support
– C++, Python, Pascal, Java
– C, Haskell, Ocaml, Blockly
– and many more
Built-in Online IDE
– Code, compile and run
– Cloud storage
– Mobile and touch screen support
Problem Set
– More than 900 tasks of various difficulty
– 55 DSE Programming exercises
– Coming Soon: DSE Database SQL exercises
– Past problems of HKOI and other competitions
School Admin Tools
– Solution and test data for DSE exercises
– Student progress tracking (assignments)
– User and group management
– Custom task hosting (Full version required)

For School Admins

Teachers can sign up for a free trial (no time limit) to experience the features of the Online Judge. A subscription fee is required to make the Online Judge available to students. For details, please refer to the following guides.

Subscription and School Admins

Basic Info, Groups and Users


Task UI and integrated IDE
(Note: DSE Exercises are also available in Chinese)
Judging results – School Admins can see the submitted code
Submission list – Submission record of other users are available
School Admin tool – Student progress tracking (assignments)