The Repeat Visitor

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

Domain

Python

Difficulty

medium

Seniority

L4

Problem

Given a list of purchase records (dicts with 'user' and 'date' in 'YYYY-MM-DD' format) and integer days, return users who made at least two purchases within a rolling window: there exist two of their purchase dates d1 <= d2 with (d2 - d1) days <= days. Return the list of user IDs sorted alphabetically.

Summary

Loyal customers come back sooner than expected.

Practice This Problem

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