Apply Discount to Prices

Problem Description

You are given a string representing a sentence and an integer discount. For each word representing a price (a sequence of digits preceded by a dollar sign), apply a discount of discount% on the price and update the word in the sentence. All updated prices should be represented with exactly two decimal places. Return a string representing the modified sentence.

Key Insights

• A word is a price if it starts with a dollar sign followed by digits.
• We need to parse each price, apply the discount, and format the result to two decimal places.
• The discount calculation involves simple arithmetic operations.
• Care must be taken to preserve the original structure of the sentence while replacing prices.

Space and Time Complexity

Time Complexity: O(n), where n is the length of the sentence since we must examine each word. Space Complexity: O(n), for storing the modified sentence.

Solution

To solve the problem, we can follow these steps:

1. Split the sentence into words based on spaces.
2. Iterate through each word and check if it matches the price format (i.e., starts with '$' followed by digits).
3. For each price word, convert the price to a numerical value, apply the discount, and format it back to a string with two decimal places.
4. Replace the original price word with the updated price in the sentence.
5. Join the words back into a single string and return it.

We use a list to collect the modified words so we can efficiently join them into a final string.

Code Solutions