[leetcode]First Unique Character in a String

class Solution:
    def firstUniqChar(self, s: str) -> int:
        charIndexDict = {}
        for i in range(len(s)):
            if s[i] in charIndexDict:
                charIndexDict[s[i]] = -1
            else:
                charIndexDict[s[i]] = i
        
        minIdx = float(‘inf‘)
        for char in charIndexDict:
            if charIndexDict[char] != -1:
                idx = charIndexDict[char]
                if idx < minIdx:
                    minIdx = idx
                    
        if minIdx == float(‘inf‘):
            return -1
        
        return minIdx