Remove Duplicate Letters

medium · verified · 52.9% accepted · 9,278 likes · top 43%

string · stack · greedy · monotonic stack

Description

Given a string s, remove duplicate letters so that every letter appears once and only once. You must make sure your result is the smallest in lexicographical order among all possible results.

Example 1:

Input: s = "bcabc"

Output: "abc"

Example 2:

Input: s = "cbacdcbc"

Output: "acdb"

Solution