How should I practice Group Names by Department?

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

Is Group Names by Department associated with Mastercard?

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

Group Names by Department

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Problem statement

You are given a matrix people. Each row contains exactly two strings:

people[i][0] is a person's name.
people[i][1] is that person's department.

Group the names by department.

Return a matrix in which each row begins with a department, followed by the names assigned to it. Order department rows by each department's first appearance in people, and preserve input order among names in the same department.

Function

groupNamesByDepartment(people: String[][]) → String[][]

Examples

Example 1

people = [["Ava","Data"],["Ben","Risk"],["Chen","Data"],["Diya","Risk"]]return = [["Data","Ava","Chen"],["Risk","Ben","Diya"]]

Data appears first, followed by Risk. Names remain in their original order within each department.

Example 2

people = [["Mina","Finance"],["Noah","Engineering"],["Omar","Finance"]]return = [["Finance","Mina","Omar"],["Engineering","Noah"]]

The Finance row is first because that department is encountered first.

Example 3

people = [["Zoe","Legal"]]return = [["Legal","Zoe"]]

A single record creates one department row.

Constraints

1 <= people.length <= 10^5.
people[i].length = 2.
Every name and department is non-empty.
The total number of characters in people is at most 10^6.