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  • The amount of money withdrawn or transferred from is less than or equal to the balance of the account.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

submission

struct Bank {
    // use hashmap for storing balance since it
    // easier to accquire multiple mutable reference
    // of values from it
    balance: std::collections::HashMap<i32, 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 {
        let balance = balance.into_iter()
            .enumerate()
            // +1 here
            .map(|(idx, bal)| (idx as i32 + 1, bal))
            .collect();
        Self { balance }
    }
    
    fn transfer(&mut self, account1: i32, account2: i32, money: i64) -> bool {
        if account1 == account2 {
            // special case same account otherwise
            // get_disjoint_mut will panic
            return self.withdraw(account1, money) && self.deposit(account1, money);
        }
        let [Some(balance1), Some(balance2)] = self.balance.get_disjoint_mut([&account1, &account2]) else {
            return false;
        };
        if *balance1 < money {
            return false;
        }
        *balance1 -= money;
        *balance2 += money;
        true
    }
    
    fn deposit(&mut self, account: i32, money: i64) -> bool {
        let Some(balance) = self.balance.get_mut(&account) else {
            return false;
        };
        *balance += money;
        true
    }
    
    fn withdraw(&mut self, account: i32, money: i64) -> bool {
        let Some(balance) = self.balance.get_mut(&account) else {
            return false;
        };
        if *balance < money {
            return false;
        }
        *balance -= 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);
 */