How to get the smallest in lexicographical order?

Question

I am doing a leetcode exercise

https://leetcode.com/problems/remove-duplicate-letters/

The question is:

# Given a string which contains only lowe         


        

Answer 1

There seems to be some misunderstanding; the example states that for the input bcabc, the expected output should be abc, not acdb, which refers to the input cbacdcbc.