PYTHON PROBLEM 139 · Intermediate

Validate a binary search tree

Confirm that all nodes obey the global binary-search-tree ordering rule.

BST · boundsBSTbounds

PROBLEM OVERVIEW

What this Python exercise asks you to practise

This scenario tests validate a binary search tree. It belongs to the Trees and Tries roadmap and uses the bst · bounds pattern.

Traversal, recursion on hierarchies, binary-search-tree rules, prefix lookup, and subtree reasoning.

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SKILL TO CARRY FORWARD

Pattern relevance

This exercise strengthens bst · bounds. Be ready to explain the input, the rule, the boundary cases, and why the chosen approach is appropriate.