LeetCode 2043. Simple Bank System Solution in Java, C++, Python & More | Explanation + Code

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].

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• The amount of money withdrawn or transferred from is less than or equal to the balance of the account.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 withdraw10.
                         // 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 transfer20.
                         // Account 5 has 30 -20 = 10, and account 1 has10 + 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.

Solutions

Solution 1: Simulation

We can use an array balance to store the balance of each account. For each operation, we simply perform the required checks and updates according to the problem statement.

For the transfer operation, we need to check whether the account numbers are valid and whether the balance is sufficient. If the conditions are met, we perform the transfer.

For the deposit operation, we only need to check whether the account number is valid, and then perform the deposit.

For the withdraw operation, we need to check whether the account number is valid and whether the balance is sufficient. If the conditions are met, we perform the withdrawal.

Each operation has a time complexity of O(1), so the overall time complexity is O(q), where q is the number of operations. The space complexity is O(1).

PythonJavaC++GoTypeScriptRust

class Bank: def __init__(self, balance: List[int]): self.balance = balance self.n = len(balance) def transfer(self, account1: int, account2: int, money: int) -> bool: if account1 > self.n or account2 > self.n or self.balance[account1 - 1] < money: return False self.balance[account1 - 1] -= money self.balance[account2 - 1] += money return True def deposit(self, account: int, money: int) -> bool: if account > self.n: return False self.balance[account - 1] += money return True def withdraw(self, account: int, money: int) -> bool: if account > self.n or self.balance[account - 1] < money: return False self.balance[account - 1] -= money return True # Your Bank object will be instantiated and called as such: # obj = Bank(balance) # param_1 = obj.transfer(account1,account2,money) # param_2 = obj.deposit(account,money) # param_3 = obj.withdraw(account,money)(code-box)

class Bank { private long[] balance; private int n; public Bank(long[] balance) { this.balance = balance; this.n = balance.length; } public boolean transfer(int account1, int account2, long money) { if (account1 > n || account2 > n || balance[account1 - 1] < money) { return false; } balance[account1 - 1] -= money; balance[account2 - 1] += money; return true; } public boolean deposit(int account, long money) { if (account > n) { return false; } balance[account - 1] += money; return true; } public boolean withdraw(int account, long money) { if (account > n || balance[account - 1] < money) { return false; } balance[account - 1] -= money; return true; } } /** * Your Bank object will be instantiated and called as such: * Bank obj = new Bank(balance); * boolean param_1 = obj.transfer(account1,account2,money); * boolean param_2 = obj.deposit(account,money); * boolean param_3 = obj.withdraw(account,money); */(code-box)

class Bank { public: vector<long long> balance; int n; Bank(vector<long long>& balance) { this->balance = balance; n = balance.size(); } bool transfer(int account1, int account2, long long money) { if (account1 > n || account2 > n || balance[account1 - 1] < money) return false; balance[account1 - 1] -= money; balance[account2 - 1] += money; return true; } bool deposit(int account, long long money) { if (account > n) return false; balance[account - 1] += money; return true; } bool withdraw(int account, long long money) { if (account > n || balance[account - 1] < money) return false; balance[account - 1] -= money; return true; } }; /** * Your Bank object will be instantiated and called as such: * Bank* obj = new Bank(balance); * bool param_1 = obj->transfer(account1,account2,money); * bool param_2 = obj->deposit(account,money); * bool param_3 = obj->withdraw(account,money); */(code-box)

type Bank struct { balance []int64 n int } func Constructor(balance []int64) Bank { return Bank{balance, len(balance)} } func (this *Bank) Transfer(account1 int, account2 int, money int64) bool { if account1 > this.n || account2 > this.n || this.balance[account1-1] < money { return false } this.balance[account1-1] -= money this.balance[account2-1] += money return true } func (this *Bank) Deposit(account int, money int64) bool { if account > this.n { return false } this.balance[account-1] += money return true } func (this *Bank) Withdraw(account int, money int64) bool { if account > this.n || this.balance[account-1] < money { return false } this.balance[account-1] -= money return true } /** * Your Bank object will be instantiated and called as such: * obj := Constructor(balance); * param_1 := obj.Transfer(account1,account2,money); * param_2 := obj.Deposit(account,money); * param_3 := obj.Withdraw(account,money); */(code-box)

class Bank { balance: number[]; constructor(balance: number[]) { this.balance = balance; } transfer(account1: number, account2: number, money: number): boolean { if ( account1 > this.balance.length || account2 > this.balance.length || money > this.balance[account1 - 1] ) return false; this.balance[account1 - 1] -= money; this.balance[account2 - 1] += money; return true; } deposit(account: number, money: number): boolean { if (account > this.balance.length) return false; this.balance[account - 1] += money; return true; } withdraw(account: number, money: number): boolean { if (account > this.balance.length || money > this.balance[account - 1]) { return false; } this.balance[account - 1] -= money; return true; } } /** * Your Bank object will be instantiated and called as such: * var obj = new Bank(balance) * var param_1 = obj.transfer(account1,account2,money) * var param_2 = obj.deposit(account,money) * var param_3 = obj.withdraw(account,money) */(code-box)

struct Bank { balance: Vec<i64>, } /** * `&self` means the method takes an immutable reference. * If you need a mutable reference, change it to `&mut self` instead. */ impl Bank { fn new(balance: Vec<i64>) -> Self { Bank { balance } } fn transfer(&mut self, account1: i32, account2: i32, money: i64) -> bool { let (account1, account2, n) = (account1 as usize, account2 as usize, self.balance.len()); if n < account1 || n < account2 { return false; } if self.balance[account1 - 1] < money { return false; } self.balance[account1 - 1] -= money; self.balance[account2 - 1] += money; true } fn deposit(&mut self, account: i32, money: i64) -> bool { let (account, n) = (account as usize, self.balance.len()); if n < account { return false; } self.balance[account - 1] += money; true } fn withdraw(&mut self, account: i32, money: i64) -> bool { let (account, n) = (account as usize, self.balance.len()); if n < account { return false; } if self.balance[account - 1] < money { return false; } self.balance[account - 1] -= money; true } }(code-box)