It was a HackerRank challenge in Java and SQL. There was a time limit of 2 hours. I completed the challenge, and the tests passed, but I didn't receive any feedback and was rejected.

There are currencies and conversions between them. Develop two methods to perform subtraction and addition with different currencies, always converting values to the left-side currency. Parsing strings should not be necessary. For example, 1 EUR = 5 BRL. Therefore, 1 BRL + 1 EUR = 6 BRL, and 1 EUR - 1 BRL = 0.8 EUR. Calculations must also be precise.

There are 3 tables: locations > companies > employees. You need to write a query to list employees in the most populous location.