AlgoDaily - Dollar Sign Deletion

Dollar Sign Deletion (Medium)

Good morning! Here's our prompt for today.

You may see this problem at Palantir, Lyft, Goldman Sachs, Flatiron Health, Confluent, Asana, Pipedrive, Grammarly, Illumio, and Zoom.

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:

1String[] input = {"f$st", "st"};
2isDollarDeleteEqual(input);
3// true
4// 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

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import org.junit.Test;
import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;
​
import static org.junit.Assert.*;
​
// solution
​
class Solution {
​
    public static boolean isDollarDeleteEqual(String[] arr) {
        // fill in
        // with solution
        return false;
    }
​
    private static String getFinalStr(String str) {
        // fill in
        // with solution
        return str;
    }
​
    // print your findings using this function!
    public static void log() {
        String[] input = new String[] {"f$st", "st"};
        System.out.println(isDollarDeleteEqual(input));

OUTPUT

Results will appear here.