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.

 from collections import OrderedDict
class Solution:
    def firstUniqChar(self, s: str) -> int:

        hash_map = OrderedDict()
        index = {}

        for i, char in enumerate(s):
            hash_map[char]=hash_map.get(char, 0) + 1
            index[char]=i

        for i, k in enumerate(hash_map.keys()):
            if hash_map[k]==1:
                return index[k]

        return -1

#         hash_map = OrderedDict()

#         for i, char in enumerate(s):
#             hash_map[char]=hash_map.get(char, 0) + 1

#         for i, k in enumerate(hash_map.keys()):
#             if hash_map[k]==1:
#                 return s.find(k)
#         return -1

First Unique Character In A String

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