How should I practice Environment Variable Store and Substitution?

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

Is Environment Variable Store and Substitution associated with Amazon?

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

Amazon● MediumFULLTIMEPHONE SCREEN

Process a sequence of environment-variable operations:

["SET", key, value] stores or overwrites a value.
["GET", key] emits the value or NULL when missing.
["PARSE", text] emits text after replacing every complete %KEY% placeholder whose key exists. Missing placeholders remain unchanged.

Substitution is one pass: replacement values are not expanded again during the same operation.

processEnvironment(operations: String[][]) → String[]

operations = [["SET","NAME","Tom"],["PARSE","Hello I am %NAME%"]]return = ["Hello I am Tom"]

The stored NAME value replaces its placeholder.

operations = [["GET","MISSING"],["PARSE","%MISSING%"]]return = ["NULL","%MISSING%"]

Missing GET and PARSE have distinct deterministic outputs.