How should I practice Group Linked Merchant Records?

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

Is Group Linked Merchant Records associated with Stripe?

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

Problem · Array

Group Linked Merchant Records

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Problem statement

You are given merchant dictionaries serialized as records. Each row contains alternating key and value strings: [key1, value1, key2, value2, ...]. Every row contains exactly one non-empty merchant_id. A row may also contain the identity fields email, phone, and address, plus arbitrary additional fields.

Two records are directly linked when they share the same non-empty value for at least one identity field with the same key. Merchant groups are the transitive closure of those direct links. Additional fields are valid input but never establish links.

Return every connected group as its merchant IDs sorted lexicographically. Sort the groups lexicographically by their complete sorted ID lists.

Function

linkedMerchantGroups(records: String[][]) → List<List<String>>

Examples

Example 1

records = [["merchant_id","m1","email","a@x.com"],["merchant_id","m2","email","a@x.com","phone","222"],["merchant_id","m3","phone","222"],["merchant_id","m4","address","4 Main"]]return = [["m1","m2","m3"],["m4"]]

m1 links to m2 by email, and m2 links to m3 by phone, so transitivity joins all three.

Example 2

records = [["merchant_id","b","note","same"],["merchant_id","a","note","same"],["merchant_id","c","email","c@x.com"]]return = [["a"],["b"],["c"]]

The shared extra field note does not establish a link.

Constraints

1 <= records.length <= 200000
Each row contains between 1 and 20 key-value pairs.
Keys and values are printable-ASCII strings of length at most 200.
Every merchant_id is non-empty and unique.
Within a record, each of merchant_id, email, phone, and address appears at most once.