How do you solve Account Balance After Rounded Purchase on LeetCode?

Account Balance After Rounded Purchase (LeetCode #2806) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(1) time complexity and O(1) space complexity. Key insight: Rounding can be efficiently calculated using mathematical formulas.

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

The optimal solution for Account Balance After Rounded Purchase runs in O(1) time and uses O(1) space. Both time and space complexity are O(1) because we are performing a constant number of operations regardless of the input size.

What is the brute force solution for Account Balance After Rounded Purchase?

The brute force approach for Account Balance After Rounded Purchase is Brute Force, with O(n) time complexity and O(1) space complexity. The brute force approach involves checking all multiples of 10 up to the purchase amount and finding the nearest one. This is straightforward but not efficient. The optimal Optimal Solution approach improves this to O(1).

What algorithm or data structure is used to solve Account Balance After Rounded Purchase?

Account Balance After Rounded Purchase uses the following concepts: Math. The recommended patterns to study are: Math, Integer Manipulation.

What are the interview tips for Account Balance After Rounded Purchase?

Always clarify the problem statement and constraints before diving into coding. Think aloud while solving to show your thought process. Consider edge cases and test your solution with them.

What are common mistakes when solving Account Balance After Rounded Purchase?

Forgetting to round up correctly when the amount is exactly halfway. Not considering edge cases like 0 or 100.

#2806

Account Balance After Rounded Purchase

Easy

MathMathInteger Manipulation

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(n)	O(1)
Space	O(1)	O(1)

💡

Intuition

Time O(1)Space O(1)

The optimal solution uses a mathematical formula to calculate the rounded amount directly, which is much more efficient than looping through multiples.

⚙️

Algorithm

3 steps

1Step 1: Calculate the rounded amount using the formula: roundedAmount = ((purchaseAmount + 5) // 10) * 10.
2Step 2: Subtract the rounded amount from the initial balance of 100.
3Step 3: Return the final balance.

solution.py6 lines

1# Full working Python code
2balance = 100
3purchaseAmount = 9
4roundedAmount = ((purchaseAmount + 5) // 10) * 10
5final_balance = balance - roundedAmount
6print(final_balance)

ℹ

Complexity note: Both time and space complexity are O(1) because we are performing a constant number of operations regardless of the input size.

1Rounding can be efficiently calculated using mathematical formulas.
2Understanding how to manipulate integers can simplify problems.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.