README.md

387. 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.

Related Topics

1. Hash Table
2. String
3. Queue
4. Count

📝 Note

1. Go through the string and store each charater occurrences in a hash table.
2. Go through the string again and check for the occurence of the current character. Return the index if the count of s[i] is 1.
3. Return -1 if non of characters appeared only once.