Currency Conversion Queries | Dataford Interview Questions

Your question is Currency Conversion Queries. Start with the requirements on the right.

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Problem

An Axon cloud platform service receives currency exchange rates and must answer multiple conversion queries. Each exchange rate defines a directed conversion, and the reverse conversion is also available at the reciprocal rate.

Implement convert_currency(rates, queries) to return the conversion multiplier for each query. Return -1.0 when no conversion path exists.

Formal Specification

rates is a list of [sourceCurrency, targetCurrency, rate], where currencies are non-empty strings and rate is a positive number.
queries is a list of [sourceCurrency, targetCurrency] pairs.
Return a list of floating-point values in query order.
A query from a currency to itself returns 1.0 if that currency appears in the exchange-rate graph. Otherwise, return -1.0.
If a path contains rates a -> b and b -> c, its conversion multiplier is the product of those rates.

Constraints

1 <= len(rates), len(queries) <= 10^4
Each currency name contains at most 8 uppercase letters
0 < rate <= 10^6
Each rate pair has distinct currencies
The exchange graph can be disconnected

Function Signature

def convert_currency(rates, queries):