Google New Grad R2 Rejection: Prefix Disjointness and Roof-Hole Board Cover

Role: Software Engineer, New Grad
Result: Rejected after R2
Report time: February 2026

Timeline

• November 10, 2025: received the OA
• December 11: R1 virtual coding; behavioral was rescheduled to December 16
• December 17: passed R1
• January 21, 2026: completed R2
• February 5: received the rejection

R2 coding 1: remove prefix conflicts

Given two arrays and an integer k, delete elements from the second list so that its first k elements share no values with the first k elements of the first list.

The source does not say whether the required output is a minimum deletion count, deleted indices, the modified list, or a feasibility decision. It also does not define behavior when fewer than k safe values remain, so no exact practice link is asserted.

R2 coding 2: cover roof holes with boards

A binary m × n matrix represents a roof, where 0 cells are holes. A repair may place a full row-length 1 × n board or a full column-length m × 1 board. Return the minimum number of boards needed to cover every hole.

The candidate attempted an exponential DFS and miscalculated its complexity. After the interview, they learned that the task maps rows and columns to a bipartite graph: every hole is an edge, and the minimum board count is the minimum vertex cover, equal to maximum matching.

Practice: Minimum Boards to Cover Roof Holes

The candidate believed this second question caused the rejection but still described Google's overall process and the Chinese interviewers as supportive.