Is Account Balance After Rounded Purchase easy or hard?

Account Balance After Rounded Purchase is classified as an Easy problem. It tests basic arithmetic reasoning, rounding rules, and clean implementation rather than complex algorithms or data structures.

Account Balance After Rounded Purchase Python/Java solution

In Python or Java, compute purchaseAmount % 10 to determine the rounding direction. Adjust the value to the nearest multiple of 10 and return 100 minus that rounded number. The implementation takes only a few lines and runs in O(1) time.

How to solve Account Balance After Rounded Purchase in O(1)?

Calculate the remainder using purchaseAmount % 10. If the remainder is at least 5, add (10 - remainder) to round up; otherwise subtract the remainder to round down. Finally compute 100 minus the rounded purchase amount to get the remaining balance. The operations are constant time.

What is the best approach for Account Balance After Rounded Purchase?

The best approach uses direct arithmetic rounding. Compute purchaseAmount % 10 to determine the nearest multiple of 10, round up when the remainder is 5 or more, then subtract the rounded value from 100. This runs in O(1) time and O(1) space and is the expected interview solution.

Is Account Balance After Rounded Purchase asked at Google/Amazon/Meta?

Account Balance After Rounded Purchase is typically categorized as an easy math or simulation problem. While not a common direct interview question at Google, Amazon, or Meta, similar rounding and arithmetic logic questions frequently appear in online assessments and coding screens.

What data structure is used in Account Balance After Rounded Purchase?

No specialized data structure is required. The problem relies purely on arithmetic operations such as modulo and conditional checks, making it a basic math and simulation problem.

What is the time complexity of Account Balance After Rounded Purchase?

The optimal solution runs in O(1) time because it performs a constant number of arithmetic operations and condition checks. Space complexity is also O(1) since no additional data structures are required.

Description Hints 2 Solution Video 4:23

2806. Account Balance After Rounded Purchase

Easy58.6% acceptance

Initially, you have a bank account balance of 100 dollars.

You are given an integer purchaseAmount representing the amount you will spend on a purchase in dollars, in other words, its price.

When making the purchase, first the purchaseAmount is rounded to the nearest multiple of 10. Let us call this value roundedAmount. Then, roundedAmount dollars are removed from your bank account.

Return an integer denoting your final bank account balance after this purchase.

Notes:

0 is considered to be a multiple of 10 in this problem.
When rounding, 5 is rounded upward (5 is rounded to 10, 15 is rounded to 20, 25 to 30, and so on).

Example 1:

Input: purchaseAmount = 9

Output: 90

Explanation:

The nearest multiple of 10 to 9 is 10. So your account balance becomes 100 - 10 = 90.

Example 2:

Input: purchaseAmount = 15

Output: 80

Explanation:

The nearest multiple of 10 to 15 is 20. So your account balance becomes 100 - 20 = 80.

Example 3:

Input: purchaseAmount = 10

Output: 90

Explanation:

10 is a multiple of 10 itself. So your account balance becomes 100 - 10 = 90.

Constraints:

0 <= purchaseAmount <= 100

Topics

Math

Hints open one at a time

Hint 1

To determine the nearest multiple of 10, we can brute force the rounded amount since there are at most 100 options. In case of multiple nearest multiples, choose the largest.

Hint 2

Another solution is observing that the rounded amount is floor((purchaseAmount + 5) / 10) * 10. Using this formula, we can calculate the account balance without having to brute force the rounded amount.

4:23

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1class Solution:
2    def accountBalanceAfterPurchase(self, purchaseAmount: int) -> int:
3        

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