2043. Simple Bank System LeetCode Solution
In this guide, you will get 2043. Simple Bank System LeetCode Solution with the best time and space complexity. The solution to Simple Bank System problem is provided in various programming languages like C++, Java, and Python. This will be helpful for you if you are preparing for placements, hackathons, interviews, or practice purposes. The solutions provided here are very easy to follow and include detailed explanations.
Table of Contents
- Problem Statement
- Complexity Analysis
- Simple Bank System solution in C++
- Simple Bank System solution in Java
- Simple Bank System solution in Python
- Additional Resources

Problem Statement of Simple Bank System
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].
Execute all the valid transactions. A transaction is valid if:
The given account number(s) are between 1 and n, and
The amount of money withdrawn or transferred from is less than or equal to the balance of the account.
Implement the Bank class:
Bank(long[] balance) Initializes the object with the 0-indexed integer array balance.
boolean transfer(int account1, int account2, long money) Transfers money dollars from the account numbered account1 to the account numbered account2. Return true if the transaction was successful, false otherwise.
boolean deposit(int account, long money) Deposit money dollars into the account numbered account. Return true if the transaction was successful, false otherwise.
boolean withdraw(int account, long money) Withdraw money dollars from the account numbered account. Return true if the transaction was successful, false otherwise.
Example 1:
Input
[“Bank”, “withdraw”, “transfer”, “deposit”, “transfer”, “withdraw”]
[[[10, 100, 20, 50, 30]], [3, 10], [5, 1, 20], [5, 20], [3, 4, 15], [10, 50]]
Output
[null, true, true, true, false, false]
Explanation
Bank bank = new Bank([10, 100, 20, 50, 30]);
bank.withdraw(3, 10); // return true, account 3 has a balance of $20, so it is valid to withdraw $10.
// Account 3 has $20 – $10 = $10.
bank.transfer(5, 1, 20); // return true, account 5 has a balance of $30, so it is valid to transfer $20.
// Account 5 has $30 – $20 = $10, and account 1 has $10 + $20 = $30.
bank.deposit(5, 20); // return true, it is valid to deposit $20 to account 5.
// Account 5 has $10 + $20 = $30.
bank.transfer(3, 4, 15); // return false, the current balance of account 3 is $10,
// so it is invalid to transfer $15 from it.
bank.withdraw(10, 50); // return false, it is invalid because account 10 does not exist.
Constraints:
n == balance.length
1 <= n, account, account1, account2 <= 105
0 <= balance[i], money <= 1012
At most 104 calls will be made to each function transfer, deposit, withdraw.
Complexity Analysis
- Time Complexity: O(1)
- Space Complexity: O(|\texttt{balance}|)
2043. Simple Bank System LeetCode Solution in C++
class Bank {
public:
Bank(vector<long long>& balance) : balance(std::move(balance)) {}
bool transfer(int account1, int account2, long long money) {
if (!isValid(account2))
return false;
return withdraw(account1, money) && deposit(account2, money);
}
bool deposit(int account, long long money) {
if (!isValid(account))
return false;
balance[account - 1] += money;
return true;
}
bool withdraw(int account, long long money) {
if (!isValid(account))
return false;
if (balance[account - 1] < money)
return false;
balance[account - 1] -= money;
return true;
}
private:
vector<long long> balance;
bool isValid(int account) {
return 1 <= account && account <= balance.size();
}
};
/* code provided by PROGIEZ */
2043. Simple Bank System LeetCode Solution in Java
public class Bank {
public Bank(long[] balance) {
this.balance = balance;
}
public boolean transfer(int account1, int account2, long money) {
if (!isValid(account2))
return false;
return withdraw(account1, money) && deposit(account2, money);
}
public boolean deposit(int account, long money) {
if (!isValid(account))
return false;
balance[account - 1] += money;
return true;
}
public boolean withdraw(int account, long money) {
if (!isValid(account))
return false;
if (balance[account - 1] < money)
return false;
balance[account - 1] -= money;
return true;
}
private long[] balance;
private boolean isValid(int account) {
return 1 <= account && account <= balance.length;
}
}
// code provided by PROGIEZ
2043. Simple Bank System LeetCode Solution in Python
class Bank:
def __init__(self, balance: list[int]):
self.balance = balance
def transfer(self, account1: int, account2: int, money: int) -> bool:
if not self._isValid(account2):
return False
return self.withdraw(account1, money) and self.deposit(account2, money)
def deposit(self, account: int, money: int) -> bool:
if not self._isValid(account):
return False
self.balance[account - 1] += money
return True
def withdraw(self, account: int, money: int) -> bool:
if not self._isValid(account):
return False
if self.balance[account - 1] < money:
return False
self.balance[account - 1] -= money
return True
def _isValid(self, account: int) -> bool:
return 1 <= account <= len(self.balance)
# code by PROGIEZ
Additional Resources
- Explore all LeetCode problem solutions at Progiez here
- Explore all problems on LeetCode website here
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