[387] First Unique Character in a String

https://leetcode.com/problems/first-unique-character-in-a-string/description/

• algorithms
• Easy (47.96%)
• Source Code: 387.first-unique-character-in-a-string.py
• Total Accepted: 252.4K
• Total Submissions: 508.1K
• Testcase Example: '"leetcode"'

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode" return 0.

s = "loveleetcode", return 2.

Note: You may assume the string contain only lowercase letters.

class Solution(object):
    def firstUniqChar(self, s):
        """
        :type s: str
        :rtype: int
        """
        arr = [0] * 26
        for i in s:
            arr[ord(i)-ord('a')] += 1
        for idx, i in enumerate(s):
            if arr[ord(i)-ord('a')] == 1:
                return idx
        return -1