Solution: Remove Duplicate Letters
Explore a greedy stack technique to remove duplicate letters from a string while ensuring the result is the lexicographically smallest possible. Understand how to track character frequencies, manage visited characters, and maintain optimal ordering with efficient operations that run in linear time.
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Statement
You are given a string, s, consisting only of lowercase English letters. Your task is to remove duplicate letters so that:
Each letter appears only once in the resulting string.
The resulting string is the smallest in lexicographical order among all possible results that satisfy the above condition.
Return the final string.
A string,
a, is considered lexicographically smaller than stringbif:
In the first position where they differ, the character in
aappears earlier in the alphabet than inb.If
ais a ...