How should I practice Ping Reply Tracking?

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

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Problem · Array

Ping Reply Tracking

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NvidiaFULLTIMEONSITE INTERVIEW

Problem statement

Track replies to a finite set of ping echo requests. For this exercise, assume request i is sent at integer time sendTimes[i] and carries the unique identifier i. The request identifiers are 0 through sendTimes.length - 1.

The parallel arrays replyIds and replyTimes describe received echo replies. Reply j names request replyIds[j] and arrives at time replyTimes[j]. The arrays may list replies in any order.

A reply is eligible only when its identifier names an existing request and its arrival time is in the inclusive interval [sendTimes[i], sendTimes[i] + timeout].
Ignore unknown identifiers, replies before a request was sent, and replies after its deadline.
When several replies are eligible for one request, use the earliest arrival time. Later duplicates have no effect.

Return one integer per request, in request-identifier order. An answered request returns its round-trip time, earliestArrival - sendTimes[i]. A request with no eligible reply returns -1. This exercise supplies the finite send and receive trace; no network access or packet construction is required.

Function

pingRoundTripTimes(sendTimes: int[], replyIds: int[], replyTimes: int[], timeout: int) → int[]

Examples

Example 1

sendTimes = [10,20,30]replyIds = [1,0,1,2]replyTimes = [25,17,22,41]timeout = 10return = [7,2,-1]

Request 1 chooses time 22 even though its time-25 reply appears earlier in the array. Request 2 times out because 41 is later than its deadline 40.

Example 2

sendTimes = [5,5]replyIds = [0,1,2,0]replyTimes = [4,5,5,5]timeout = 0return = [0,0]

With a zero timeout, only replies exactly at the send time qualify. The early reply and unknown identifier are ignored.

Example 3

sendTimes = [100,50]replyIds = []replyTimes = []timeout = 8return = [-1,-1]

No received replies means both requests time out, regardless of send-time order.

Constraints

1 <= sendTimes.length <= 10^5.
0 <= replyIds.length = replyTimes.length <= 10^5.
0 <= sendTimes[i], replyTimes[j] <= 10^9.
-1 <= replyIds[j] <= 10^5.
0 <= timeout <= 10^6.
Send times need not be sorted or unique.