Google 2026 New Grad SWE R1: Binary-Tree LCA and N-ary Follow-Up

Role: Software Engineer, New Grad
Result: Waitlisted after R1
Report time: November 2025
Application: Referral

Coding interview

The main problem was the standard lowest common ancestor problem for two nodes in a binary tree.

The follow-up changed the binary tree into an N-ary tree. The candidate finished the main problem quickly but initially did not understand what needed to change for the follow-up. After clarification and a hint from the interviewer, they adjusted the solution and completed it.

Practice: Lowest Common Ancestor in an N-ary Tree