Max KLA Words with 3 Keys | Dataford Interview Questions

The keyboard have only 3 keys, K,L,A and performs 3 operations ctrl-A(select all), crtl-C(copy), ctrl-V(paste). Return the maximum number of KLA words that can be formed for a given N.

Asked in the Code-pair technical stage. The SQL version uses input rows and candidate operation sequences, where invalid candidates must be ignored.

Write a PostgreSQL query to return the maximum valid result for every requested input.

Output

One row per requested input N.
Return n and max_kla_words.
Include requested inputs without valid candidates with a value of 0.
Sort by n ascending.

Schema

keyboard_inputs

Column	Type	Description
input_idPK	INT	Identifier for the input case
n	INT	Number of keyboard operations allowed
requested	BOOLEAN	Whether this input must appear in the output

candidate_sequences

Column	Type	Description
sequence_idPK	INT	Identifier for a candidate operation sequence
input_id	INT	Input case associated with the candidate
operation_sequence	VARCHAR(120)	Operations used by the candidate
kla_words	INT	Number of KLA words produced
is_valid	BOOLEAN	Whether the candidate is valid

Your question is Max KLA Words with 3 Keys. Start with the requirements and the two tables in the Question tab.

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