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1272. Invalid Transactions

My accepted Python solution to LeetCode problem 1272, Invalid Transactions, running in 50ms.

  • Difficulty: Medium
  • Python
  • Runtime 50ms
  • Memory 18.3MB

Read the problem on LeetCode View on GitHub

The problem statement is LeetCode’s and stays on their site. What follows is my accepted solution.

Python

Accepted on LeetCode — runtime 50ms, memory 18.3MB, accepted 2026-01-02.

python
class Solution:
    def invalidTransactions(self, transactions: List[str]) -> List[str]:
        from collections import defaultdict
        
        # Parse transactions
        parsed = []
        for i, t in enumerate(transactions):
            name, time, amount, city = t.split(',')
            parsed.append((name, int(time), int(amount), city, i))
        
        invalid = set()
        
        # Check each transaction
        name_transactions = defaultdict(list)
        for name, time, amount, city, idx in parsed:
            name_transactions[name].append((time, city, idx))
        
        for name, time, amount, city, idx in parsed:
            # Invalid if amount > 1000
            if amount > 1000:
                invalid.add(idx)
            
            # Check for transactions with same name in different city within 60 minutes
            for other_time, other_city, other_idx in name_transactions[name]:
                if city != other_city and abs(time - other_time) <= 60:
                    invalid.add(idx)
                    invalid.add(other_idx)
        
        return [transactions[i] for i in invalid]

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