How should I practice Decode and Store Strings?

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

Is Decode and Store Strings associated with Airbnb?

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

Decode and Store Strings

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Problem statement

Decode every string in encoded and append its decoded value to an initially empty in-memory list, processing inputs in their given order. Return that complete stored list.

For this practice exercise, each encoded string uses a flat run-length format: a token is a positive decimal count followed by one lowercase ASCII letter. Expand the token by repeating that letter exactly count times, and concatenate the expanded tokens. For example, 3a2b decodes to aaabb.

Every input string is valid. Counts have no leading zero, and there are no brackets, nesting, separators, escape rules or error records. An empty encoded string decodes to an empty string and still occupies one position in the stored list. Duplicate inputs are retained independently.

Function

decodeAndStore(encoded: String[]) → String[]

Examples

Example 1

encoded = ["3a2b","1z"]return = ["aaabb","z"]

The first input contains two runs; the second contains one letter.

Example 2

encoded = ["","2a1b","2a1b"]return = ["","aab","aab"]

An empty string retains its position, and duplicate inputs are stored separately.

Example 3

encoded = ["12x1y"]return = ["xxxxxxxxxxxxy"]

A multi-digit count belongs to one token, followed by the next token.

Constraints

0 <= encoded.length <= 1000.
Every token has a count from 1 through 1000 followed by one lowercase ASCII letter.
The total encoded character count is at most 100000.
The total decoded character count is at most 10000.
Every encoded string follows the stated token grammar or is empty.