My first instinct was to just BFS and track parent and depth for each node, which works, but I spent too long second-guessing whether siblings meant same parent or just same level.
Clarify the definitions of siblings and cousins in a binary tree, then propose a solution that finds the depth and parent of each node. Use these to determine the relationship: siblings share the same parent, cousins share the same depth but different parents, otherwise they are unrelated.
Pro tip: Mention edge cases like one node being an ancestor of the other, or the nodes being the same, and discuss time/space complexity trade-offs between BFS and DFS approaches.
Define siblings as nodes with the same parent, and cousins as nodes at the same depth but with different parents. Confirm with the interviewer if these definitions align with their expectations.
Decide between BFS (level-order) or DFS to find the depth and parent of each node. BFS naturally tracks depth, while DFS can be adapted with parameters.
Traverse the tree to locate both nodes, recording their depth and parent. If a node is not found, handle appropriately.
Compare the depth and parent of the two nodes: if same parent, they are siblings; if same depth but different parents, they are cousins; otherwise, they are unrelated (e.g., ancestor/descendant or different branches).
State the time complexity (O(n) for traversal) and space complexity (O(n) for BFS queue or O(h) for DFS recursion) and discuss potential optimizations.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.