How should I practice Account Balance Manager Part 2 - Reject Overdrafts?

Start by reading the full statement, solve the visible examples, then compare the pattern against related Stripe onsite interview problems in FastPrep.

Is Account Balance Manager Part 2 - Reject Overdrafts associated with Stripe?

FastPrep tags this as a Stripe onsite interview coding practice problem when the problem catalog has that company and stage context.

Problem · Hash Table

Account Balance Manager Part 2 - Reject Overdrafts

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Problem statement

Source note: July 26, 2026 — 🌺 I re-audited the original author-written sources and rebuilt this practice version from the available interview reports. It is about a 25% match to the available source. The Stripe coding-round context, Account Balance / Bank Transaction topic, and three-question progression come directly from the sources. A supporting report also confirms that the final follow-up passes a platform account whose funds may cover negative accounts. The individual Part 2 objective, overdraft rule, original function signature, runnable input format, constraints, examples, and edge-case behavior were not shown, so FastPrep supplied them as a bounded practice contract rather than presenting them as source facts. If a more complete author-written source becomes available, I will continue refining this problem step by step.

Practice sequence

Part 1: Calculate Totals
Part 2: Reject Overdrafts (you are here)
Part 3: Platform Coverage

What the interview report shared

The coding round centered on Account Balance / Bank Transaction and contained three questions.

Practice contract

For this exercise, assume transactions arrive in order as account_id,amount strings and every account starts with a balance of 0.

Reject a transaction when applying it would make that account's balance negative, and leave the balance unchanged.
Otherwise, accept the transaction and update the balance. A resulting balance of exactly 0 is allowed.

Return the rejected transaction strings in their original order.

Function

rejectedTransactions(transactions: String[]) → String[]

Examples

Example 1

transactions = ["account_A,100", "account_A,-150", "account_B,50", "account_A,-80", "account_B,-100"]return = ["account_A,-150", "account_B,-100"]

Step 1: account_A +100 -> 100 (ok). Step 2: account_A -150 -> would be -50 (REJECT). Step 3: account_B +50 -> 50 (ok). Step 4: account_A -80 -> 100-80=20 (ok). Step 5: account_B -100 -> would be -50 (REJECT). The two rejected transactions are returned in order.

Example 2

transactions = ["account_A,40", "account_A,-40", "account_A,-1"]return = ["account_A,-1"]

account_A +40 -> 40 (ok). account_A -40 -> exactly 0, which is allowed (ok). account_A -1 -> would be -1 (REJECT). Only the last transaction is rejected.

Constraints

Each transaction is "account_id,amount" with an integer amount.
Process in order; reject a transaction whose application would make the balance strictly negative.
Deposits are always allowed; a result of exactly 0 is allowed.
A rejected transaction does not change any balance.
Return rejected transactions in order as "account_id,amount".