Implement Table Aggregation
Company: Notion
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: easy
Interview Round: Technical Screen
You are given a table represented as a list of rows. Each row contains:
- `key`: a string identifying a group
- `value`: an integer
Write a function that aggregates the table by `key` and returns, for each distinct key, the sum of all corresponding `value`s.
Example:
Input rows:
- `(A, 3)`
- `(B, 5)`
- `(A, 2)`
- `(B, 1)`
- `(C, 4)`
Output:
- `(A, 5)`
- `(B, 6)`
- `(C, 4)`
The output may be returned in any order unless otherwise specified.
Follow-up discussion:
1. How would you extend the implementation so that it can support other aggregation functions such as `MAX` in addition to `SUM`?
2. If the table is too large to fit into memory, how would you process it efficiently?
Quick Answer: This question evaluates a candidate's ability to perform data aggregation and manipulate basic data structures by grouping records by key and combining numeric values.