Practice/Capital One/Leetcode 2043. Simple Bank System

Leetcode 2043. Simple Bank System

CodingMust

Problem

You need to implement a banking system that manages multiple customer accounts. The system should support three fundamental banking operations: transferring money between accounts, depositing money into an account, and withdrawing money from an account.

Your task is to create a Bank class that is initialized with an array of starting balances for each account. The accounts are numbered starting from 1 (not 0), so the first element in the balance array corresponds to account 1, the second element to account 2, and so on.

Each operation should validate that:

• The account number(s) involved actually exist in the bank
• For withdrawals and transfers, the source account has sufficient funds
• The operation completes successfully by updating the relevant account balances

If an operation cannot be completed due to invalid account numbers or insufficient funds, it should return false without modifying any balances. Otherwise, it should perform the operation and return true.

Requirements

1. Implement a constructor that accepts an array of initial account balances
2. Implement a transfer(account1, account2, money) method that moves money from account1 to account2
3. Implement a deposit(account, money) method that adds money to the specified account
4. Implement a withdraw(account, money) method that removes money from the specified account
5. All methods should return true on success and false on failure
6. Account numbers are 1-indexed (first account is 1, not 0)
7. Validate all account numbers before performing operations
8. Ensure sufficient funds exist before withdrawing or transferring

Constraints

• 1 ≤ balance.length ≤ 105
• 0 ≤ balance[i] ≤ 1012
• 1 ≤ account, account1, account2 ≤ balance.length
• account1 ≠ account2 (for transfer operations)
• 1 ≤ money ≤ 1012
• At most 104 calls will be made to each method

Examples

Example 1:

` Input: Bank bank = new Bank([100, 200, 300]) bank.withdraw(1, 50) bank.deposit(2, 100) bank.transfer(3, 1, 150)

Output: [true, true, true]

Explanation:

• Account 1 starts with 100, withdrawing 50 leaves 50 (success)
• Account 2 gets 100 deposited, going from 200 to 300 (success)
• Account 3 has 300, transfers 150 to account 1 (success)
• Final balances: [200, 300, 150] `

Example 2:

` Input: Bank bank = new Bank([500, 1000]) bank.withdraw(3, 100) bank.deposit(2, 50) bank.transfer(2, 1, 2000)

Output: [false, true, false]

Explanation:

• Account 3 doesn't exist (only 2 accounts), withdrawal fails
• Account 2 deposit of 50 succeeds (balance becomes 1050)
• Account 2 only has 1050, cannot transfer 2000 (fails)
• Final balances: [500, 1050] `

Example 3:

` Input: Bank bank = new Bank([100]) bank.withdraw(1, 100) bank.withdraw(1, 10)

Output: [true, false]

Explanation:

• First withdrawal empties account 1 (balance becomes 0)
• Second withdrawal fails because account 1 has 0 balance `