如何获得字典顺序中最小的？

我正在做leetcode练习

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

问题是：

# Given a string which contains only lowercase letters, remove duplicate
# letters so that every letter appear once and only once. You must make
# sure your result is the smallest in lexicographical order among all possible results.
#
# Example:
# Given "bcabc"
# Return "abc"
#
# Given "cbacdcbc"
# Return "acdb"

我不太确定what is the smallest in lexicographical order以及为什么给定“cbacdcbc”那么答案将是“acdb”

感谢您提前的答复:)

The smallest lexicographical order is an order relation where string s is smaller than t, given the first character of s (s₁) is smaller than the first character of t (t₁), or in case they are equivalent, the second character, etc.

So aaabbb小于aaac因为虽然前三个字符相等，但第四个字符b小于第四个字符c.

For cbacdcbc，有多种选择，因为b and c是重复项，您可以决定删除哪些重复项。这导致：

cbacdcbc = adbc
cbacdcbc = adcb
cbacdcbc = badc
cbacdcbc = badc
...
  

since adbc < adcb，因此你不能简单地回答你脑海中出现的第一个答案。