How should I practice Email Subscription Scheduler?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Stripe onsite interview problems in FastPrep.

Is Email Subscription Scheduler associated with Stripe?

FastPrep tags this as a Stripe onsite interview coding practice problem when the problem catalog has that company and stage context.

Problem · String

Email Subscription Scheduler

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Problem statement

You are given subscription records for a group of users and a schedule of lifecycle emails. Produce the email timeline in chronological order.

Each entry in users is formatted as "name,plan,begin_day,duration". The subscription expires on begin_day + duration.

Each entry in schedule is formatted as "key,title":

start sends the email on begin_day.
A negative integer such as -15 sends the email that many days before expiry.
end sends the email on the expiry day.

Part 1: Scheduled emails

Generate all scheduled emails for every user.

Part 2: Plan changes

Each plan-change record in changes is formatted as "name,change_day,plan,new_plan". Emit a Changed email on change_day. Scheduled emails after that day use the new plan; the expiry day does not change.

Part 3: Renewals

Each renewal record is formatted as "name,change_day,extension,days". Emit a Renewed email on change_day, extend the user’s expiry by days, and schedule the remaining lifecycle emails from the new expiry.

Return one line per email in the format "day: [title] Subscription for name (plan)", ordered by day. When several scheduled emails share a day, preserve their order in schedule. The supplied test data does not place a change and a scheduled email on the same day.

Function

sendSubscriptionEmails(users: String[], schedule: String[], changes: String[]) → String[]

Examples

Example 1

users = ["A,X,0,30", "B,Y,1,15"]schedule = ["start,Welcome", "-15,Upcoming expiration", "end,Expired"]changes = []return = ["0: [Welcome] Subscription for A (X)", "1: [Welcome] Subscription for B (Y)", "1: [Upcoming expiration] Subscription for B (Y)", "15: [Upcoming expiration] Subscription for A (X)", "16: [Expired] Subscription for B (Y)", "30: [Expired] Subscription for A (X)"]

This is Part 1 from the source: B’s welcome and 15-day reminder both occur on day 1, while A’s reminder occurs on day 15.

Example 2

users = ["A,X,0,30", "B,Y,1,15"]schedule = ["start,Welcome", "-15,Upcoming expiration", "end,Expired"]changes = ["A,5,plan,Y"]return = ["0: [Welcome] Subscription for A (X)", "1: [Welcome] Subscription for B (Y)", "1: [Upcoming expiration] Subscription for B (Y)", "5: [Changed] Subscription for A (Y)", "15: [Upcoming expiration] Subscription for A (Y)", "16: [Expired] Subscription for B (Y)", "30: [Expired] Subscription for A (Y)"]

This is the source’s Part 2 timeline: A changes from X to Y on day 5, so A’s later reminder and expiry use Y.

Example 3

users = ["A,X,0,30", "B,Y,1,15"]schedule = ["start,Welcome", "-15,Upcoming expiration", "end,Expired"]changes = ["B,3,extension,15", "A,5,plan,Y"]return = ["0: [Welcome] Subscription for A (X)", "1: [Welcome] Subscription for B (Y)", "1: [Upcoming expiration] Subscription for B (Y)", "3: [Renewed] Subscription for B (Y)", "5: [Changed] Subscription for A (Y)", "15: [Upcoming expiration] Subscription for A (Y)", "16: [Upcoming expiration] Subscription for B (Y)", "30: [Expired] Subscription for A (Y)", "31: [Expired] Subscription for B (Y)"]

This is the source’s Part 3 timeline. B’s original expiry is day 16; extending it by 15 days moves it to day 31, so the new 15-day reminder is day 16.

Constraints

1 <= users.length <= 100.
User names are unique, and every referenced change names an existing user.
0 <= begin_day <= 10^6 and 15 <= duration <= 10^6.
schedule contains the source-backed start, -15, and end entries, with unique keys.
A user has at most one plan change and at most one renewal; change days are strictly between that user’s begin and expiry days.
No change day coincides with one of that user’s scheduled-email days.
The callable signature, CSV-style record encoding, bounds, and deterministic tie handling are FastPrep practice scaffolding; the interview report did not specify them.