LeetCode: Removing Stars From a String

Remove stars from a string using a stack approach.

Solution

Create a stack of characters to contain the answer.

Loop through each character in the string. If the character is a star (*), pop the last character from the stack. Otherwise, append the character to the stack.

Finally, join the characters in the stack to form the resulting string without stars.

class Solution:
    def removeStars(self, s: str) -> str:
        answer = []

        for c in s:
            if c == "*":
                answer.pop()
            else:
                answer.append(c)

        return "".join(answer)

Note: I attempted this problem with a two-pointer solution, just to compare performance. That solution times out on large test cases. In this example, you move through the string, tracking the last non-star character with one pointer and the current character with another pointer.