Data Merging (Gym Sessions)
Problem statement
Implement a method mergeData(sessions) that returns a unified view of each user's activities by merging gym session data.
Merging Rules
- Duration: Sum up the duration fields for the same user.
- Equipment: Combine all equipment used, de-duplicate them, and sort alphabetically.
- Order: The output order must match the earliest occurrence of each user in the input.
Example
const sessions = [
{ user: 1, duration: 10, equipment: ['bench'] },
{ user: 1, duration: 20, equipment: ['bike'] }
];
mergeData(sessions); // [{ user: 1, duration: 30, equipment: ['bench', 'bike'] }]How to approach Data Merging (Gym Sessions)
The strategy an interviewer expects you to reach for.
A strong solution for Data Merging (Gym Sessions) starts with the invariant: what should always be true after each loop step or recursive call? Once that invariant is clear, the implementation is usually small. Initialize the state, process each input item, update the state, and return the final value. After coding, walk through one normal case and one edge case. This catches most bugs and gives the interviewer confidence that you understand the trade-offs.
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