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Quick Summary

Aggregate financial transaction records per user while skipping empty fields.
Process all entries in chronological order using their timestamp field.
Return final ad delivery and payment totals for each user, sorted alphabetically.

What This Tests

Hash-based aggregation and state tracking
Sorting by custom keys and time complexity management
String parsing and null/empty value handling
Real-world data simulation and pipeline design

Common Patterns

Hashing

Sorting

Test Cases

Input

Output

Expected