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Simple Bank System

Difficulty: Medium

Problem Description

You have been tasked with writing a program for a popular bank that will automate all its incoming transactions (transfer, deposit, and withdraw). The bank has n accounts numbered from 1 to n. The initial balance of each account is stored in a 0-indexed integer array balance, with the (i + 1)th account having an initial balance of balance[i]. You need to implement a Bank class with methods to execute valid transactions.

Key Insights

  • Each account is uniquely identified by its index, and transactions can only occur between valid accounts.
  • A transaction is valid if:
    • The account numbers are in the valid range.
    • The withdrawing or transferring amount does not exceed the account's balance.
  • The operations involve updating balances atomically to ensure correctness.

Space and Time Complexity

Time Complexity: O(1) for deposit and withdraw operations, O(1) for transfer operations (assuming direct access to balances). Space Complexity: O(n) for storing the balances of the accounts.

Solution

The solution involves creating a Bank class that initializes with an array of balances. The class will have three methods: transfer, deposit, and withdraw. Each method checks if the transaction is valid based on the conditions provided and updates the balances accordingly. The balance array allows for O(1) access and modification, making the operations efficient.

Code Solutions

class Bank:
    def __init__(self, balance: List[int]):
        self.balance = balance  # Store the initial balances

    def transfer(self, account1: int, account2: int, money: int) -> bool:
        # Check if account numbers are valid and if account1 has enough balance
        if 1 <= account1 <= len(self.balance) and 1 <= account2 <= len(self.balance) and self.balance[account1 - 1] >= money:
            self.balance[account1 - 1] -= money  # Deduct money from account1
            self.balance[account2 - 1] += money  # Add money to account2
            return True
        return False

    def deposit(self, account: int, money: int) -> bool:
        # Check if account number is valid
        if 1 <= account <= len(self.balance):
            self.balance[account - 1] += money  # Add money to the account
            return True
        return False

    def withdraw(self, account: int, money: int) -> bool:
        # Check if account number is valid and if there is enough balance
        if 1 <= account <= len(self.balance) and self.balance[account - 1] >= money:
            self.balance[account - 1] -= money  # Deduct money from the account
            return True
        return False
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