How should I practice Rolling CSAT Tracker?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Decagon phone screen problems in FastPrep.

Is Rolling CSAT Tracker associated with Decagon?

FastPrep tags this as a Decagon phone screen coding practice problem when the problem catalog has that company and stage context.

Rolling CSAT Tracker

Decagon● MediumFULLTIMEPHONE SCREEN

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Problem statement

Process timestamped customer-satisfaction operations in nondecreasing time order. ADD t score records a score from 1 through 5. QUERY t asks for the average of scores whose timestamps lie in [t-windowSize+1, t].

Return one reduced sum/count fraction per query, or EMPTY when the active window has no scores.

Function

rollingCsat(operations: String[], windowSize: int) → String[]

Examples

Example 1

operations = ["ADD 1 5","ADD 3 3","QUERY 3","QUERY 6"]windowSize = 5return = ["4/1","3/1"]

At time 3 both scores are active; at time 6 only the score from time 3 remains.

Example 2

operations = ["QUERY 2","ADD 2 4","QUERY 2"]windowSize = 3return = ["EMPTY","4/1"]

The tracker distinguishes an empty window from a numeric average.

Example 3

operations = ["ADD 0 1","ADD 1 2","ADD 2 5","QUERY 2"]windowSize = 3return = ["8/3"]

The exact rational average is returned without floating-point rounding.

Constraints

1 <= operations.length <= 2 * 10^5.
1 <= windowSize <= 10^9.
Timestamps are nonnegative and nondecreasing; scores are integers from 1 through 5.