Remove Duplicates from Grid

Problem Overview

You are given an m×n grid representing a Connect-4-style game board (initially all zeros). Implement two methods: 1. drop(color, col): Drop a piece of the given color (e.g., 'Y', 'R', 'B') into the specified column. The piece falls to the lowest empty row in that column (gravity). Return the current…

• 3 candidate-reported follow-ups — the exact probes interviewers asked, with the trigger for each
• The rest of the problem statement — full requirements, constraints, and edge cases
• Approach and trade-offs — what passing candidates did, and the mistakes that sink people