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First Unique Character in a String
EasyData StructuresDescription
Given a string `s`, find the first non-repeating character in it and return its index. If it does not exist, return `-1`.
Example 1
Input: s = "leetcode"
Output: 0
Example 2
Input: s = "loveleetcode"
Output: 2
Example 3
Input: s = "aabb"
Output: -1
Constraints
- 1 <= s.length <= 10^5
- s consists of only lowercase English letters.
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