Find First Duplicate Transaction | Dataford Interview Questions

Given a list of transactions, identify the first transaction that appears more than once and return its index.

Return the index of the repeated occurrence, meaning the position where the duplicate is first detected. Return -1 if every transaction is unique. Implement first_repeated_transaction(transactions), where transactions is a list of hashable transaction identifiers and the result is an integer.

Constraints

0 <= len(transactions) <= 10^4
Each transaction identifier is hashable
Return the index of the first repeated occurrence
Return -1 when all transactions are unique

Function Signature

def first_repeated_transaction(transactions):

Your question is Find First Duplicate Transaction. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

Problem

Given a list of transactions, identify the first transaction that appears more than once and return its index.

Constraints

0 <= len(transactions) <= 10^4
Each transaction identifier is hashable
Return the index of the first repeated occurrence
Return -1 when all transactions are unique

Function Signature

def first_repeated_transaction(transactions):

Your question is Find First Duplicate Transaction. Start with the requirements in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.