Medium

Quiz

#316 Remove Duplicate Letters

APPROACH

Given a string s, remove duplicate characters so that each character appears exactly once. Among all valid results, return the lexicographically smallest one.

Example 1:

Input: s = "bcabc"

Output: "abc"

Example 2:

Input: s = "cbacdcbc"

Output: "acdb"

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What is the optimal approach for this problem?