Here is the interview question prompt, presented for reference.

You're given an array of strings containing alphabetical characters and certain $ characters. A $ represents a DELETE action whereby the character before it is deleted.

Each of these strings will be run through a method to operate on the $ DELETE action. We want to find out if the final string is the same for all of them. Let's take an example:

String[] input = {"f$st", "st"};
isDollarDeleteEqual(input);
// true
// true because both become "st"

let input = ["f$st", "st"];
isDollarDeleteEqual(input);
// true
// true because both become "st"

input = ["f$st", "st"]
is_dollar_delete_equal(input)
# True
# True because both become 'st'

std::vector<std::string> input = {"f$st", "st"};
isDollarDeleteEqual(input);
// true
// true because both become "st"

string[] input = {"f$st", "st"};
IsDollarDeleteEqual(input);
// true
// true because both become "st"

input := []string{"f$st", "st"}
isDollarDeleteEqual(input)
// true
// true because both become "st"

Can you find a solution in O(n) time and constant space?

Constraints

• The input arrays can be of any size
• Every string has at least a single character
• The string will consist of dollar signs and lowercase alphabets
• Expected overall time complexity : O(n)
• Expected space complexity : O(n) for good solution, O(1) for asymptotically optimal solution

You can see the full challenge with visuals at this link.