"""

First Unique Character in a String

Given a string, find the first non-repeating character and return its index.

If no unique character exists, return -1.

Reference: https://leetcode.com/problems/first-unique-character-in-a-string/

Complexity:

Time: O(n^2) worst case due to nested comparisons

Space: O(n) for the banned list

"""

from __future__ import annotations

def first_unique_char(text: str) -> int:

"""Find the index of the first non-repeating character in a string.

Args:

text: The input string to search.

Returns:

The index of the first unique character, or -1 if none exists.

Examples:

>>> first_unique_char("leetcode")

0

"""

if len(text) == 1:

return 0

banned: list[str] = []

for index in range(len(text)):

if (

all(text[index] != text[other] for other in range(index + 1, len(text)))

and text[index] not in banned

):

return index

else:

banned.append(text[index])

return -1