| Haystacks | https://codeforces.com/contest/2055/problem/E | 中等 | 好题 |
| Scarecrow | https://codeforces.com/contest/2055/problem/D | 中等 | 模拟 |
| Balanced Tree | https://codeforces.com/contest/2062/problem/D | 中等 | 树 |
| Tree Destruction | https://codeforces.com/contest/2050/problem/G | 中等 | 树 |
| DFS Checker (Hard Version) | https://codeforces.com/contest/2002/problem/D2 | 中等 | 树思维 |
| Maximize the Root | https://codeforces.com/contest/1997/problem/D | 简单 | 树 |
| Paint the Tree | https://codeforces.com/contest/1975/problem/D | 简单 | 树 |
| Tree Compass | https://codeforces.com/contest/1943/problem/C | 中等 | 树构造 |
| The Game (Easy Version) | https://codeforces.com/contest/2062/problem/E1 | 中等 | 博弈 |
| Everything Nim | https://codeforces.com/contest/1966/problem/C | 简单 | 博弈 |
| Prefix GCD | https://codeforces.com/contest/2013/problem/E | 中等 | 数论 |
| Small GCD | https://codeforces.com/contest/1900/problem/D | 中等 | 数论 |
| Minimize the Difference | https://codeforces.com/contest/2013/problem/D | 中等 | 二分 |
| Yet Another Monster Fight | https://codeforces.com/contest/1901/problem/D | 中等 | 二分 |
| Med-imize | https://codeforces.com/contest/1993/problem/D | 中等 | 中位数 |
| Unique Median | https://codeforces.com/problemset/problem/2056/D | 中等 | 中位数好题 |
| Determine Winning Islands in Race | https://codeforces.com/contest/1998/problem/D | 中等 | 图论 |
| Time Travel | https://codeforces.com/contest/1887/problem/B | 中等 | 图论 |
| Eliminating Balls With Merging (Easy Version) | https://codeforces.com/contest/1998/problem/E1 | 中等 | 贪心消除重复计算 |
| Shrink-Reverse | https://codeforces.com/contest/1923/problem/F | 困难 | 后缀数组 |
| Ones and Twos | https://codeforces.com/contest/1896/problem/D | 简单 | 数据结构 |
| Last Man Standing | https://codeforces.com/contest/1879/problem/F | 困难 | 数据结构 |
| Most Different Tree | https://codeforces.com/contest/1867/problem/F | 困难 | 哈希 |
| Flower-like Pseudotree | https://codeforces.com/contest/1869/problem/F | 困难 | 分类讨论恶心 |