This question evaluates proficiency in tree algorithms and hierarchical data comparison, including simultaneous traversal, subtree sizing, key-based node identity, and time/space complexity reasoning, and is commonly asked to assess algorithmic problem-solving and trade-off analysis when comparing structured datasets.

You are given two rooted catalog trees. Each node has a unique string key among its siblings and an associated value. Compare the two trees and return the total number of differing nodes under these rules: (