Validate Binary Search Tree

Trees · BST · Carry valid bounds downward · Stretch · about 26 min

Why it matters

Passing constraints down a tree is more reliable than checking only parent-child pairs.

How it connects

Tree recursion now carries context: a node must obey limits created by every ancestor.

Try first

Why is checking only “left < parent < right” not enough?

Interview cue

Ancestor bounds capture the whole BST rule, not just immediate parent relationships.