Lessons Learned

Full Euler tour with RMQ solves LCA in $O(1)$ or $O(\log n)$ per query. This is one of the standard LCA algorithms. Other LCA methods include binary lifting ($O(\log n)$ per query with simpler code) and Tarjan's offline algorithm ($O(1)$ amortized but requires knowing all queries upfront).

Choose based on constraints: full tour for online queries with fast responses, binary lifting for simpler implementation.