Sorting Environmental Data | Dataford Interview Questions

ERM Digital receives environmental monitoring records from multiple sites. Implement a function that returns the records in the required review order without modifying the original input list.

Sort records using these criteria, in order:

Pollutant priority, according to the supplied pollutant_priority list. Earlier pollutants have higher priority.
Measured value in descending order.
timestamp in ascending chronological order. Timestamps use the format YYYY-MM-DDTHH:MM:SSZ and are in UTC.
site in ascending lexicographical order.

Formal Specification

Implement sort_environmental_data(points, pollutant_priority).

points is a list of dictionaries with string fields site, pollutant, and timestamp, plus a numeric field value.
pollutant_priority is a list of pollutant names. Every record's pollutant appears exactly once in this list.
Return a new list containing the same dictionaries in the required order.
Do not mutate points.

Constraints

1 <= len(points) <= 100,000
1 <= len(pollutant_priority) <= 100
0 <= point['value'] <= 1,000,000,000
Every record pollutant appears exactly once in pollutant_priority
Timestamps are valid UTC strings in fixed-width ISO format

Function Signature

def sort_environmental_data(points, pollutant_priority):

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