387. First Unique Character in a String LeetCode Solution | Easy Approach

First Unique Character in a String 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 <= 105
• s consists of only lowercase English letters.

First Unique Character in a String Solutions

✅Time: O(n)
✅Space: O(n)

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