Faces in the Crowd

A medium Python interview practice problem on DataDriven. Write and execute real python code with instant feedback.

Domain

Python

Difficulty

medium

Seniority

L3

Problem

You are replaying a site's visit log one day at a time, where each entry in `daily_visitors` is that day's list of visitor names and a name can repeat within a day. For each day, report how many people showed up who had never appeared on any earlier day.

Summary

New arrivals keep showing up. Count the ones you have not seen yet.

Practice This Problem

Solve this Python problem with real code execution. DataDriven runs your Python code in a real environment and checks it automatically.