Hot100: Same Tree (Synchronous Recursion / BFS ACERS Guide)
Subtitle / Summary The real challenge in LeetCode 100 is not “can you traverse a tree”, but “can you compare two trees node by node in lockstep”. This ACERS guide explains the synchronous-recursion contract, the queue-of-pairs BFS variant, and why the pattern matters in real engineering work. Reading time: 9-11 min Tags: Hot100, binary tree, DFS, BFS, tree comparison SEO keywords: Hot100, Same Tree, binary tree comparison, synchronous recursion, BFS, LeetCode 100 Meta description: A systematic guide to LeetCode 100 from synchronous recursion to pairwise BFS comparison, with engineering scenarios and runnable multi-language implementations. Target Readers Hot100 learners who want to build a stable “compare two trees together” template Developers who can write DFS on one tree but get confused once two trees must be checked in parallel Engineers who need structural-equivalence checks for config trees, component trees, or syntax trees Background / Motivation When many people first see LeetCode 100, the instinct is: ...