2043. Simple Bank System

Problem

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• The amount of money withdrawn or transferred from is less than or equal to the balance of the account.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 <= 10^5

• 0 <= balance[i], money <= 10^12

• At most 10^4 calls will be made to each function transfer, deposit, withdraw.

Solution (Java)

class Bank {
    private final long[] accounts;

    public Bank(long[] balance) {
        accounts = balance;
    }

    private boolean validate(int account, long money, boolean withdraw) {
        return account < accounts.length && (!withdraw || accounts[account] >= money);
    }

    public boolean transfer(int account1, int account2, long money) {
        if (validate(account1 - 1, money, true) && validate(account2 - 1, 0, false)) {
            accounts[account1 - 1] -= money;
            accounts[account2 - 1] += money;
            return true;
        }
        return false;
    }

    public boolean deposit(int account, long money) {
        if (validate(account - 1, money, false)) {
            accounts[account - 1] += money;
            return true;
        }
        return false;
    }

    public boolean withdraw(int account, long money) {
        if (validate(account - 1, money, true)) {
            accounts[account - 1] -= money;
            return true;
        }
        return false;
    }
}

/**
 * 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);
 */

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).