2351. First Letter to Appear Twice
Given a string \(s\) consisting of lowercase English letters, return the first letter to appear twice.
Note:
- A letter \(a\) appears twice before another letter \(b\) if the second occurrence of \(a\) is before the second occurrence of \(b\).
- \(s\) will contain at least one letter that appears twice.
https://leetcode.cn/problems/first-letter-to-appear-twice
标签：1.1,twice,second,letter,一题,before,LeetCode,appear From： https://www.cnblogs.com/kirin-dev/p/LeetCode_1-1.html