Start a Thread

Subscribe You’re not receiving notifications from this thread.

Dollar Sign Deletion (Main Thread)

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:

const input = ["f$st", "st"]
// true
// true because both become "st"

Given the below function signature, can you find a solution in O(n) time and constant space?

function isDollarDeleteEqual(arr) {


  • 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)

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

Challenges • Asked almost 2 years ago by Hardik

Jake from AlgoDaily Commented on Sep 04, 2019:

This is the main discussion thread generated for Dollar Sign Deletion.

Hardik Commented on Sep 04, 2019:

Test case 1 and 2 are both same yet it is shown that their results are different.

lazycoder Commented on Mar 11, 2020:

['f$ec', 'ec'] should return true

['f$ec', 'ec'] should return false
These 2 test cases are contradictory.

Rahat Zaman Commented on Feb 05, 2021:

Yes, we have now fixed this problem.

yorkcook13 Commented on Mar 24, 2021:

I can't figure out why my code doesn't work. It works when I try it in, is it because it doesn't make the time constraint?? Thanks!

function isDollarDeleteEqual(arr) {
let mapped = => getFinalStr(item));
return mapped.every(item => item === mapped[0]);
function getFinalStr(str) {
let arr = str.split('');

for(i =0; i < arr.length; i++) {
if(arr[i] === '$') {
arr.splice(i-1, 2);

return arr.join('');