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387. First Unique Character In A String

Hash Table String Queue Counting

Problem - 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

Explanation:

The character 'l' at index 0 is the first character that does not occur at any other index.

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.

Solutions

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

Submission Stats:

  • Runtime: 47 ms (88.88%)
  • Memory: 18 MB (83.01%)