Coding

Tree-Based

Asked at

Juspay

Meesho

1Give yourself 5 minutes

2Answer out loud, not in your head

3Then compare with the answer below

Stuck? Show a way to structure it+

01Clarify node structure and requested result.
02Choose a traversal that exposes needed child information.
03Define exactly what each recursive return means.
04Handle null nodes and unbalanced depth.

Reference answer

“Tree-Based” is only a topic label, not enough information to code safely. Ask for the input representation, whether the structure is guaranteed acyclic, and the desired result. For a subtree computation, use postorder DFS and make the return contract precise, such as “the maximum value in this subtree” or “whether this subtree is valid.” For a path or level question, explain why preorder, postorder, or BFS fits. Never use node values as visited keys when duplicates are possible; use node identity for graph-like inputs. A standard full traversal is O(n) time, with O(h) call-stack space for DFS or O(w) queue space for BFS. Test null, a leaf, a completely skewed tree, and duplicate labels. This clarifying step is the correct answer until the interviewer provides a concrete property.

Then expect these follow-ups

What makes a DFS return value composable?
Tests: recursion
How would you avoid stack overflow?
Tests: iterative traversal

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