Adding Spaces to a String Python Solution

lcpy gen -n 2109   # by problem number
lcpy gen -s adding_spaces_to_a_string   # by problem name

Input: s = "LeetcodeHelpsMeLearn", spaces = [8,13,15]
Output: "Leetcode Helps Me Learn"

Input: s = "icodeinpython", spaces = [1,5,7,9]
Output: "i code in py thon"

Input: s = "spacing", spaces = [0,1,2,3,4,5,6]
Output: " s p a c i n g"

class Solution:
    # Time: O(n + m) where n = len(s), m = len(spaces)
    # Space: O(n + m) for the output
    def add_spaces(self, s: str, spaces: list[int]) -> str:
        parts: list[str] = []
        prev = 0
        for idx in spaces:
            parts.append(s[prev:idx])
            prev = idx
        parts.append(s[prev:])
        return " ".join(parts)