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 prefix of b, then a is considered smaller.

Constraints:

• $1 \leq$ s.length $\leq 10^3$

• s consists of lowercase English letters.

Let’s take a moment to make sure you’ve correctly understood the problem. The quiz below helps you check if you’re solving the correct problem:

We have a game for you to play. Rearrange the logical building blocks to develop a clearer understanding of how to solve this problem.

Implement your solution in the following coding playground.