Decoded String at Index Python Solution

lcpy gen -n 880   # by problem number
lcpy gen -s decoded_string_at_index   # by problem name

Input: s = "leet2code3", k = 10
Output: "o"
Explanation: The decoded string is "leetleetcodeleetleetcodeleetleetcode".
The 10th letter in the string is "o".

Input: s = "ha22", k = 5
Output: "h"
Explanation: The decoded string is "hahahaha".
The 5th letter is "h".

Input: s = "a2345678999999999999999", k = 1
Output: "a"
Explanation: The decoded string is "a" repeated 8301530446056247680 times.
The 1st letter is "a".

class Solution:
    # Time: O(n)
    # Space: O(1)
    def decode_at_index(self, s: str, k: int) -> str:
        size = 0
        for char in s:
            size = size * int(char) if char.isdigit() else size + 1

        for char in reversed(s):
            k %= size
            if k == 0 and char.isalpha():
                return char
            if char.isdigit():
                size //= int(char)
            else:
                size -= 1
        raise ValueError("k out of range")