| Problem Name | Online Judge | Year | Contest | Difficulty Level | |
|---|---|---|---|---|---|
| 1 | A Star not a Tree? | PKU | 2 | ||
| 2 | Run Away | PKU | 3 | ||
| 3 | Super Star | PKU | 4 | ||
| 4 | Studying For Exams | Live Archive | 2016 | North America - Rocky Mountain | 6 |
| 5 | Hongcow Buys a Deck of Cards | Codeforces | Codeforces Round #385 (Div. 1) & Codeforces Round #385 (Div. 2) | 7 | |
| 6 | Commentator problem | Codeforces | Codeforces Beta Round #2 | 7 | |
| 7 | Corridor | Codeforces | Yandex.Algorithm 2011 Qualification 2 | 9 |