387. First Unique Character in a String

Easy

---

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.

class Solution:
    def firstUniqChar(self, s: str) -> int:
        counter = Counter(s)
        for i in range(len(s)):
            if counter[s[i]] == 1:
                return i
        return -1