You've learned three powerful tree techniques:
HLD: Decomposes tree into heavy chains for path queries
Centroid Decomposition: Divide-and-conquer with levels for distance queries
Treaps: Randomized BST with split/merge for dynamic sequences
Euler Tour: Flattens subtrees to ranges for subtree queries These techniques turn hard tree problems into manageable range queries. Practice combining them, many competition problems require exactly that. You now have a complete toolkit for tree-based data structures. The next step is practice: solve problems, make mistakes, and build intuition.