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Formatted question description: https://leetcode.ca/all/2043.html

# 2043. Simple Bank System (Medium)

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• The amount of money withdrawn or transferred from is less than or equal to the balance of the account.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.

## Solution 1.

• // OJ: https://leetcode.com/problems/simple-bank-system/
// Time: O(1) for all
// Space: O(N)
class Bank {
vector<long long> balance;
bool valid(int account) {
return account > 0 && account <= balance.size();
}
bool enough(int account, long long money) {
return balance[account - 1] >= money;
}
public:
Bank(vector<long long>& balance) : balance(balance) {}
bool transfer(int from, int to, long long money) {
if (valid(from) && valid(to) && enough(from, money)) {
balance[from - 1] -= money;
balance[to - 1] += money;
return true;
}
return false;
}
bool deposit(int account, long long money) {
if (valid(account)) {
balance[account - 1] += money;
return true;
}
return false;
}
bool withdraw(int account, long long money) {
if (valid(account) && enough(account, money)) {
balance[account - 1] -= money;
return true;
}
return false;
}
};

• 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)

############

# 2043. Simple Bank System
# https://leetcode.com/problems/simple-bank-system/

class Bank:

def __init__(self, balance: List[int]):
self.banks = [0] + balance
self.n = len(balance)

def transfer(self, account1: int, account2: int, money: int) -> bool:
if 1 <= account1 <= self.n and 1 <= account2 <= self.n and self.banks[account1] >= money:
self.banks[account1] -= money
self.banks[account2] += money
return True

return False

def deposit(self, account: int, money: int) -> bool:
if 1 <= account <= self.n:
self.banks[account] += money
return True

return False

def withdraw(self, account: int, money: int) -> bool:
if 1 <= account <= self.n and self.banks[account] >= money:
self.banks[account] -= money
return True

return False

# 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)


• 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);
*/

• 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);
*/


• 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)
*/


• 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
}
}

/**
* Your Bank object will be instantiated and called as such:
* let obj = Bank::new(balance);
* let ret_1: bool = obj.transfer(account1, account2, money);
* let ret_2: bool = obj.deposit(account, money);
* let ret_3: bool = obj.withdraw(account, money);
*/


We can also implement transfer using withdraw and deposit.

• bool transfer(int from, int to, long long money) {
return valid(to) && withdraw(from, money) && deposit(to, money);
}

• 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)

############

# 2043. Simple Bank System
# https://leetcode.com/problems/simple-bank-system/

class Bank:

def __init__(self, balance: List[int]):
self.banks = [0] + balance
self.n = len(balance)

def transfer(self, account1: int, account2: int, money: int) -> bool:
if 1 <= account1 <= self.n and 1 <= account2 <= self.n and self.banks[account1] >= money:
self.banks[account1] -= money
self.banks[account2] += money
return True

return False

def deposit(self, account: int, money: int) -> bool:
if 1 <= account <= self.n:
self.banks[account] += money
return True

return False

def withdraw(self, account: int, money: int) -> bool:
if 1 <= account <= self.n and self.banks[account] >= money:
self.banks[account] -= money
return True

return False

# 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)


• 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);
*/

• 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);
*/


• 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)
*/


• 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
}
}

/**
* Your Bank object will be instantiated and called as such:
* let obj = Bank::new(balance);
* let ret_1: bool = obj.transfer(account1, account2, money);
* let ret_2: bool = obj.deposit(account, money);
* let ret_3: bool = obj.withdraw(account, money);
*/


## Discuss

https://leetcode.com/problems/simple-bank-system/discuss/1525207/C%2B%2B-Straightforward