Card Provider Detection | Dataford Interview Questions

If you had to build a system where a user inputs a credit card number, detect which provider it belongs to based on given credit card number ranges.

Asked in the Live DSA round stage. It was the second DSA question, related to using TreeMap in Java, and was solved verbally.

Implement classify_provider(card_number, ranges). card_number is a digit string. ranges is a list of [start, end, provider] entries sorted by start, with non-overlapping inclusive ranges. Return the matching provider, or "Unknown" if no range contains the number.

Examples:

"4111111111111111" with Visa and Mastercard ranges returns "Visa".
"6011111111111117" returns "Unknown" when it matches no range.

Constraints: Card numbers contain 1 to 19 digits; 1 <= len(ranges) <= 1000.

Constraints

card_number contains 1 to 19 decimal digits
1 <= len(ranges) <= 1000
Each range is [start, end, provider]
start and end are non-negative integers with start <= end
ranges are sorted by start and do not overlap
provider is a non-empty string

Function Signature

def classify_provider(card_number, ranges):

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Problem