First Unique Character
Beginner
Return the index of the first character in s that appears exactly once in the whole string, or -1 if every character repeats (or the string is empty).
Examples
Example 1
Input:
first_unique_character('leetcode')
Output:
0
l at index 0 appears once.
Example 2
Input:
first_unique_character('aabb')
Output:
-1
Every character repeats.
Constraints
0 <= len(s) <= 3 * 10**5scontains lower-case letters.
Theory
Go to TheoryKeywords
dsa-sheethashingcounting-with-dictionaries
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