| Difficulty | Problems | Hints | Solution |
|---|---|---|---|
| 1600 | CF1056D | Smaller subtrees mean easier constraints. | Editorial |
| 1700 | CF1592C | The xor-sum of every connected component is fixed. Use this fact. | Editorial |
| 1800 | CF1083A | Classic way of thinking a path on the tree: fix the important point. Then consider your DP | Editorial |
| 1900 | CF1076E | Notice that you only have to answer the question after all updates. How can you maintain the changes during traversal? (Bonus: Answer the queries of points' values while updating.) | Editorial |
| 1900 | CF739B | The controlling points clearly form a segment in the tree. You just need to find the endpoint. | Editorial |
| 1900 | CF500D | When you think about the sum / expectation of something, you can break it into parts and calculate their contribution. | Editorial |
| 2000 | CF1010D | You can find the value first, and then try to figure out which leaves change the answer. | Editorial |
| 2100 | CF1152D | Try solving the problem in a smaller tree. What information should be necessary for your DP function? | Editorial |
| 2100 | CF576B | Construct a graph using the permutation. For the final tree, construct an edge first, what edges should it produce? Summarize and find the necessary conditions. | Editorial |
| 2100 | CF802K | When considering a subtree, there are two possible situations: you return to the root to get to the other subtrees; you never return. | Editorial |
| 2200 | CF1615D | How can you calculate the xor-sum of a path on the tree? Then, what kind of information does the conditions offer you? | Editorial |