Multi-Language (Coding): Remove Duplicates from String Test

The problem requires removing all duplicate characters from a given string Str while keeping the order of the remaining characters intact. The output should be a string that contains each character of the input string only once. To solve the problem, the solution needs to iterate through the input string and keep track of the characters seen so far in a hash set. If a character is not already present in the hash set, it is added to the output string, otherwise it is skipped. The output string at the end will contain only the unique characters in the order they appeared in the input string.