Implement bank balance operations

Question

Design and implement a Bank account class that supports the operations Deposit(amount), Withdraw(amount), and CashBack(percent). Ensure balance updates correctly, prevent overdrafts, and return the updated balance after each operation.

Bank Balance Operations

Design a bank account that processes a sequence of operations and returns the resulting balance after each one.

You are given a list of operations. Each operation is a pair [opType, value] where opType is:

• 0 = Deposit value dollars into the account.
• 1 = Withdraw value dollars from the account.
• 2 = CashBack: add value percent of the current balance back to the account (integer cashback, floor division).

The account starts with a balance of 0. Apply the operations in order and, for each one, append the resulting balance to an output list.

Validation rules (an operation that violates a rule is REJECTED — the balance is left unchanged and you append -1 for that operation):

• Deposit: value must be positive (> 0).
• Withdraw: value must be positive and must not exceed the current balance (no overdrafts).
• CashBack: value (the percent) must be non-negative (>= 0).

Return the list of results, one entry per operation.

Example: operations [[0,100],[1,30],[2,10]] -> deposit 100 (balance 100), withdraw 30 (balance 70), cashback 10% of 70 = 7 (balance 77) -> returns [100, 70, 77].

Constraints

• 0 <= operations.length <= 10^4
• Each operation is a pair [opType, value] with opType in {0, 1, 2}
• 0 <= value <= 10^6
• Account starts at balance 0
• A rejected operation (invalid amount or overdraft) leaves the balance unchanged and yields -1
• CashBack uses integer floor division: added amount = balance * percent // 100

Hints

1. Maintain a single running balance and append the new balance after each accepted operation.
2. Withdraw must be rejected (append -1, leave balance unchanged) whenever the requested amount exceeds the current balance — this is how you prevent overdrafts.
3. For cashback, compute balance * percent // 100 using integer (floor) division and add it to the balance.