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387. First Unique Character in a String

Difficulty Topics

Description

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.

Solution

first-unique-character-in-a-string.py
class Solution:
    def firstUniqChar(self, s: str) -> int:
        mp = collections.Counter(s)

        for i, x in enumerate(s):
            if mp[x] == 1:
                return i

        return -1