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Grokking the Coding Interview Patterns in JavaScript

Solution: Remove Duplicate Letters

Understand how to apply a greedy stack-based algorithm to remove duplicate letters from a string, ensuring each letter appears once and the result is lexicographically smallest. Explore the use of frequency maps, visited sets, and stack manipulations to solve this problem efficiently with O(n) time complexity.

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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:

  1. Each letter appears only once in the resulting string.

  2. 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 string b if:

  • In the first position where they differ, the character in a appears earlier in the alphabet than in b.

  • If a is a ...