Aggregate expenses by person, trip, and category

Q: Aggregate expenses by person, trip, and category

This question evaluates a candidate's ability to perform efficient data aggregation, use associative data structures (maps/dictionaries), and reason about time and space complexity when processing large collections of records.

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Question

Problem

You are given a list of expense records. Each record has:

employee_id (string)
trip_id (string)
category (string, e.g., MEAL , HOTEL , TRANSPORT )
amount (integer)

Implement functions to compute aggregated totals:

Per-employee total

Return total spend for each employee_id .

Per-trip breakdown (for one employee)

Given an employee_id , return total spend per trip_id .

Per-category breakdown (for one employee)

Given an employee_id , return total spend per category .

Input/Output expectations

Input: an array/list of expense records.
Output: maps/dictionaries for each query type.

Constraints

Up to 10^6 expense records.
Aim for efficient time complexity; avoid re-scanning the full list for every query.

Aggregate expenses by person, trip, and category

Quick Overview

Problem

Input/Output expectations

Constraints

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