B. Buffoon

Codeforces

IDCF10234B

Time1000ms

Memory256MB

Difficulty—

English · Original

Formal · Original

The complete problemset is available on http://maratona.ime.usp.br/primfase19/provas/competicao/maratona_en.pdf [samples]

**Definitions** Let $ T = (V, E) $ be a tree with $ |V| = n $, $ V = \{1, 2, \dots, n\} $. Let $ C \subseteq V $, $ |C| = k $, be the set of colored vertices, with $ C = \{a_1, a_2, \dots, a_k\} $. Let $ U = V \setminus C $ be the set of uncolored vertices. For a vertex $ x \in U $, let $ T_x $ denote the tree rooted at $ x $. Let $ \text{children}(x) $ be the set of children of $ x $ in $ T_x $. For each child $ c \in \text{children}(x) $, let $ T_c $ be the subtree rooted at $ c $. **Constraints** 1. $ 2 \le n \le 2 \cdot 10^5 $ 2. $ 1 \le k < n $ 3. $ C \subset V $, all $ a_i \in V $ are distinct 4. $ T $ is connected and acyclic **Objective** A vertex $ x \in U $ is *interesting* if, for every child $ c \in \text{children}(x) $, the subtree $ T_c $ contains at least one vertex from $ C $. Find the set $ I = \{ x \in U \mid x \text{ is interesting} \} $, and output $ |I| $ and the elements of $ I $ in ascending order.

API Response (JSON)

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