Google Early Career R1: Cheapest Common Ancestor and Project Discussion

Role: Software Engineer, Early Career
Result: Final outcome not disclosed
Report time: January 2026

Behavioral and project discussion

The interviewer asked about a recent project that was both challenging and interesting, then followed up on the problems the candidate encountered.

Coding: cheapest common ancestor

Every node in a tree has a price and references to its parent and children. Given two different nodes, find the lowest-priced node among all of their common ancestors.

The candidate:

1. Discussed a brute-force approach.
2. Defined the TreeNode class needed by the solution.
3. Implemented the base solution.
4. Analyzed time complexity.
5. Dry-ran an example.
6. Proposed test cases and edge cases.
7. Discussed ideas and complexity for an optimal solution when time ran out.

Practice: Cheapest Common Ancestor

The source does not preserve the exact tree-root guarantee or tie rule beyond the canonical practice assumptions documented on FastPrep.