Google New Grad R1 Rejection: Babylon Tile-Stack Game Simulation

Role: Software Engineer, New Grad
Result: Rejected after R1
Report time: December 2025

Coding: Babylon game

Two players alternate moves using 12 tiles:

• Four colors: Y, W, G, and B
• Three tiles of each color
• Initially, every tile is its own stack of height one

A legal move places one entire stack on another when either:

1. The two stack heights are equal, or
2. The two top colors are equal.

After merging, the new height is the sum of the old heights, and the top color is the top color of the stack placed above.

The last player able to make a legal move wins. A player with no legal merge loses.

The candidate had to implement the game directly in a shared document. The interviewer offered hints, but the candidate did not finish and was rejected several days later.

A commenter proposed memoized DFS over game states: if any legal move leads to a losing state for the opponent, the current state is winning. The candidate confirmed that approach.

Practice: Can the Current Player Win Babylon?