Tree lifting — binary lifting

2^k ancestor jumps — LCA/path queries.

Try this in Python

LOG = 3  # toy
# up[v][k] would store 2^k-th ancestor; build omitted for brevity
up = [[-1, -1, -1] for _ in range(5)]
print("Store up[v][k] for k in 0..LOG-1; answer queries by jumping powers of two")

Key takeaways

• Rooted tree + parent.
• Dynamic — link-cut.
• LOG = bit length n.