How should I practice Wait Time for the Next Customer?

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

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Wait Time for the Next Customer

Google● MediumNEW GRADONSITE INTERVIEW

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Problem statement

There are n servers. Server i takes exactly serviceTimes[i] time units for every customer. All servers are idle at time 0, and waitingPeople customers are ahead of you in one first-come, first-served queue.

Whenever a server is free and the queue is nonempty, the next customer starts immediately. Return the earliest time at which you start service. If a server is already available for you at time 0, return 0.

When several servers finish at the same time, all of those service slots become available at that time.

Function

waitTimeForNextCustomer(serviceTimes: int[], waitingPeople: long) → long

Examples

Example 1

serviceTimes = [5,10]waitingPeople = 0return = 0

Both servers are idle, so you start immediately.

Example 2

serviceTimes = [5,10]waitingPeople = 2return = 5

The two waiting customers start at time zero. The five-unit server frees first.

Example 3

serviceTimes = [3,7]waitingPeople = 5return = 9

Customers ahead start at times 0,0,3,6,7; you take the next slot at time 9.

Constraints

1 <= serviceTimes.length <= 100000.
1 <= serviceTimes[i] <= 1000000.
0 <= waitingPeople <= 10^12.