How do you solve Simple Bank System on LeetCode?

Simple Bank System (LeetCode #2043) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(n) time complexity and O(n) space complexity. Key insight: Direct indexing allows for efficient access and updates to account balances.

What is the brute force solution for Simple Bank System?

The brute force approach for Simple Bank System is Brute Force, with O(n²) time complexity and O(1) space complexity. In this approach, we directly check the validity of each transaction by accessing the accounts and their balances. It's straightforward but inefficient as it involves multiple checks for each transaction. The optimal Optimal Solution approach improves this to O(n).

What algorithm or data structure is used to solve Simple Bank System?

Simple Bank System uses the following concepts: Array, Hash Table, Design, Simulation. The recommended patterns to study are: Hash Map, Array.

What are the interview tips for Simple Bank System?

Always validate inputs before processing transactions. Think about edge cases, such as transferring from an empty account. Practice explaining your thought process as you code.

What are common mistakes when solving Simple Bank System?

Failing to check if account numbers are within valid range. Not updating balances correctly after a successful transaction.

#2043

Simple Bank System

Medium

ArrayHash TableDesignSimulationHash MapArray

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n²)	O(n)
Space	O(1)	O(n)

💡

Intuition

Time O(n)Space O(n)

This approach uses direct indexing to access account balances, ensuring efficient transactions with constant time complexity for each operation. We only check the necessary conditions without redundant checks.

⚙️

Algorithm

3 steps

1Step 1: Initialize the bank with the given balance array.
2Step 2: For each transaction, validate the account numbers and check the balance only when necessary.
3Step 3: Update the balances directly if the transaction is valid.

solution.py22 lines

1class Bank:
2    def __init__(self, balance):
3        self.balance = balance
4
5    def transfer(self, account1, account2, money):
6        if 1 <= account1 <= len(self.balance) and 1 <= account2 <= len(self.balance) and self.balance[account1 - 1] >= money:
7            self.balance[account1 - 1] -= money
8            self.balance[account2 - 1] += money
9            return True
10        return False
11
12    def deposit(self, account, money):
13        if 1 <= account <= len(self.balance):
14            self.balance[account - 1] += money
15            return True
16        return False
17
18    def withdraw(self, account, money):
19        if 1 <= account <= len(self.balance) and self.balance[account - 1] >= money:
20            self.balance[account - 1] -= money
21            return True
22        return False

ℹ

Complexity note: The complexity is O(n) for initializing the bank and O(1) for each transaction, as we directly access the balance array without nested loops.

1Direct indexing allows for efficient access and updates to account balances.
2Validating transactions requires careful checks on account numbers and balances.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.