The problem didn't say binary tree, which I noticed pretty quickly and went with an N-ary structure where each node holds a list of children.
Start by defining a clear tree node structure with a value and child pointers, then implement a recursive depth-first traversal that sums the node's value with the sums of its subtrees. Discuss the time and space complexity, and mention iterative alternatives for robustness.
Pro tip: At Citadel, interviewers value clean, efficient code and awareness of edge cases like null roots and deep recursion; proactively mention potential stack overflow and how to mitigate it with an iterative approach.
Ask whether the tree is binary or n-ary, if values can be negative, and if the tree is guaranteed to be non-empty. This shows attention to detail and avoids assumptions.
Design a simple class or struct with a value field and a list of children (or left/right pointers for binary trees). Keep it minimal and extensible.
Write a recursive function that returns 0 for a null node, otherwise returns node.value + sum of children. Explain the base case and recursive step clearly.
State that time complexity is O(n) and space complexity is O(h) for recursion, where h is tree height. Discuss handling of empty tree, single node, and skewed tree.
If time permits, mention an iterative solution using a stack to avoid recursion depth issues, demonstrating versatility.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.