Checkpoint: midpoint mock round
Round one
A warm-up on lists, then a tree problem with two things to track at once. 45 minutes.
Two problems, 45 minutes for both. Aim to spend around 15 on the first. Neither has a lesson above it and neither is a NeetCode 150 problem, so nothing here is something you have seen.
Warm-up: Reverse a Segment
Reverse only the nodes between two 1-indexed positions, leaving the rest of the list alone. You have reversed a whole list and reversed fixed-size groups; this is the piece in between. Think about which references you need to hold before you start rewiring.
Main: Cousins in a Tree
Two nodes are cousins when they sit at the same depth and do not share a parent. The tree here has any number of children per node rather than exactly two. Decide what each node needs to know about the path above it before you pick a traversal.