Model the employee hierarchy as a tree and perform a traversal (DFS or BFS) starting from the target employee, summing importance values as you visit each node. Use a hash map to quickly look up employees by id, and handle potential cycles or invalid ids gracefully.
Pro tip: Mention that you would clarify assumptions about the input (e.g., whether the hierarchy is guaranteed to be a tree, if ids are unique, and if there are cycles) before coding, and discuss trade-offs between recursive and iterative approaches to avoid stack overflow for deep hierarchies.
Ask about input size, whether the hierarchy is a tree (no cycles), if all subordinate ids are valid, and if the target employee exists. Confirm the expected output type.
Use a hash map to map employee id to employee object for O(1) lookup. Use a stack (iterative DFS) or queue (BFS) to traverse subordinates, or recursion if depth is manageable.
Start from the target employee, add their importance to a running total, then push all direct subordinates onto the stack/queue. Continue until no more subordinates, summing importance along the way.
Consider cases where the target employee has no subordinates, the id is invalid, or there are cycles (if not guaranteed a tree). Use a visited set to avoid infinite loops if cycles are possible.
Time complexity is O(N) where N is number of employees in the subtree, space O(N) for the map and traversal. Walk through a small example to verify correctness.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.