unreasonably effective

you can be sloppy, as long as you are rigorous

LeetCode 387: First Unique Character in a String

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The first character in the string that appears once is our answer. So, we use two passes: (1) Create the map {char -> count} (2) Find first character having count = 1.

Time: \mathcal{O}(n), space: \mathcal{O}(\texttt{alphabet-size}).

class Solution:
    def firstUniqChar(self, s: str) -> int:
        s_map = {}
        for c in s:
            s_map[c] = s_map.get(c, 0) + 1

        for i, c in enumerate(s):
            if s_map[c] == 1:
                return i
        
        return -1

tanvirdotzaman

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