I contribute to the National Olympiad in Informatics – Philippines. I help write and test problems, and help train the Philippine team to the IOI. I talk more about this in Helping out in our NOI.

Back when we didn’t have dedicated artists, I made art for some problems. Here’s the header for Sorting the Planets:

A flat drawing of some planets in a row.


Here are my problems used for public NOI.PH rounds:


From NOI.PH 2023 Finals. A string combinatorics problem.

Makafeeling Ka

From NOI.PH 2023 Finals. An interactive substring query problem.

Ang Talon ni Maria Cristina

From NOI.PH 2023 Finals. An ad hoc array modification problem.


From NOI.PH 2023 Eliminations. A combinatorics problem.

Abakoda Round 3

From Abakoda 2021. A round of four math problems.


From NOI.PH 2021 Finals. An ad hoc problem.

Functional Alchemy

From NOI.PH 2020 Finals. An ad hoc problem.

Partial Reduplication

From NOI.PH 2020 Eliminations. A simple string processing problem.

Pakain ng Pahiyas 2

From NOI.PH 2020 Eliminations. A math problem that involves some counting.

Sorting the Planets

From NOI.PH 2019 Finals. A challenging ad hoc problem that can be solved mostly through clever observations.

Exchange Gift

From NOI.PH 2019 Eliminations. A data structure problem about careful implementation.


After writing reflections for math contests, I decided to write reflections for programming contests I joined as well. These cover my junior and senior years in high school:

2017 NOI.PH Finals Reflections
  NOI.PH Team Round Reflections
2018 DISCS PRO Reflections
  NOI.PH Finals Reflections
  IOI Reflections