unique.py

#Given a string `s`, find the first non-repeating character in it and return its index. If it does not exist, return `-1`.
def firstUniqChar(s):
    """
    :type s: str
    :rtype: int
    """
    char_index = {}
    for i, char in enumerate(s):
        if char in char_index:
            char_index[char] = float('inf')
        else:
            char_index[char] = i
    
    min_index = min(char_index.values())
    return min_index if min_index != float('inf') else -1

print(firstUniqChar('leetcode'))      # Output: 0
print(firstUniqChar("loveleetcode"))  # Output: 2
print(firstUniqChar("aabb"))          # Output: -1