Practice · 3 of 3

Marked Nodes in a Subtree

CHALLENGE

Difficulty: advanced+25 XP

**Bài toán.** Rooted tree (root 1). q ops: TOG v toggles the mark on node v; CNT v prints the number of marked nodes in subtree(v). **Constraints:** 1 ≤ n, q ≤ 200 000. BIT over tin positions.

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