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Grokking the Coding Interview Patterns in Go

Solution: Remove Duplicate Letters

Explore the stack pattern to solve the problem of removing duplicate letters from a string while ensuring the result is lexicographically smallest. This lesson guides you through a greedy algorithm that uses frequency tracking and stack operations in Go. Understand how to maintain character order efficiently and implement the solution with optimal time and space 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 ...