Apply Discount to Prices

Links

Go to my solution
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My Thoughts

What Went Well
Despite having issues with edge cases, I completed this question in a reasonable amount of time.

What Went Wrong
While attempting to solve this question, I tried googling for operations to simplify my solution but came up empty-handed. Fortunately, I was able to implement it without the help of external resources.

What I Learned
I refreshed my memory on string formatting for decimal numbers.

How I Can Improve
I can continue to practice using built-in functions and review other submissions to gain a new perspective on how to approach this problem.

Comments
This challenge was fun, but it had cheap edge cases and unnecessarily dirty data, but overall a nice problem to practice lots of essential coding concepts and built-in functions.

Solution Statistics

Time Spent Coding
17 minutes

Time Complexity
O(n²) - This implementation nests an O(n + n) operation inside of an O(n) operation, which means in the worst case, we would have an O(n * 2n) runtime, which simplifies to O(n²) because we ignore multiples of n.

Space Complexity
O(1) - Two new variables are created and do not depend on the length of the sentence, resulting in the O(1) space complexity.

Runtime Beats
67.50% of other submissions

Memory Beats
84.88% of other sumbissions

Solution

class Solution:
    def discountPrices(self, sentence: str, discount: int) -> str:
        # Seperate the sentence by spaces into an array
        sentence = sentence.split()         # O(n)

        # Iterate through each word/phrase in the sentence
        for i in range(len(sentence)):      # O(n)
            num = sentence[i]               # O(1)

            # Check for constraint 1
            if num[0] == "$":               # O(1)
                # Lots of edge cases can be solved simply by placing the following
                # in a try-and-accept block, if any error is met, then continue
                try:
                    # Check for constraint 2
                    # If the number has more than ten digits, then continue
                    # We must convert it into an integer and then a string because of how
                    # very large numbers are represented
                    # Ex. 1e9 = 1,000,000,000
                    if len(str(int(num[1:]))) > 10: continue       # O(n + n)

                    # Compute the discounted price
                    num = float(num[1:])            # O(n)
                    num -= (num * discount/100)     # O(1)

                    # Repace the price in the sentence with the new one
                    # The ":.2f" format makes sure that there is always two decimal
                    # points of accuracy included when converted into a string
                    sentence[i] = f"${num:.2f}"     # O(1)
                except:
                    continue

        # Join the sentence back together, separate each element by a space
        return " ".join(sentence)