Good morning! Here's our prompt for today.

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

Try to solve this here or in Interactive Mode.

How do I practice this challenge?

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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.*;

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// solution

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class Solution {

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    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));

    }

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Here's our guided, illustrated walk-through.

How do I use this guide?