Account Balance After Rounded Purchase

Problem Description

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).

Examples

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.

Constraints

• 0 <= purchaseAmount <= 100

Solution for 1713. Account Balance After Rounded Purchase

Intuition

The problem is asking to find the nearest multiple of 10 to the given purchaseAmount and subtract that value from the initial account balance of 100 dollars.

Approach

To find the nearest multiple of 10, we can take the remainder of the purchaseAmount when divided by 10. If the remainder is less than 5, then the nearest multiple of 10 will be obtained by subtracting the remainder from the purchaseAmount. Otherwise, we need to add the difference between 10 and the remainder to the purchaseAmount to get the nearest multiple of 10.

Code in Different Languages

Python

Written by @agarwalhimanshugaya

          class Solution:
 def accountBalanceAfterPurchase(self, purchaseAmount: int) -> int:
     rem = purchaseAmount % 10
     if rem < 5:
         purchaseAmount = purchaseAmount - rem
     else:
         purchaseAmount = purchaseAmount + (10 - rem)

     return 100 - purchaseAmount

Java

Written by @agarwalhimanshugaya

       public class Solution {
 public int accountBalanceAfterPurchase(int purchaseAmount) {
     int rem = purchaseAmount % 10;
     if (rem < 5)
         purchaseAmount = purchaseAmount - rem;
     else
         purchaseAmount = purchaseAmount + (10 - rem);

     return (100 - purchaseAmount);
 }
};

C++

Written by @agarwalhimanshugaya

 class Solution {
public:
 int accountBalanceAfterPurchase(int p) {
     int rem=p%10;
     if(rem<5)
         p=p-rem;
     else
         p=p+(10-rem);
     
     return (100-p);
 }
};

Complexity Analysis

• Time Complexity: $O(1)$
• Space Complexity: $O(1)$

References

• LeetCode Problem: Account Balance After Rounded Purchase
• Solution Link: LeetCode Solution