394. Decode String

https://leetcode.com/problems/decode-string/

Python

from collections import deque


class Solution:
    def decodeString(self, s: str) -> str:
        stack = []
        for c in range(len(s)):
            if s[c] != ']':
                stack.append(s[c])
                continue

            num, letters = deque(), deque()

            while stack[-1] != '[':
                letters.appendleft(stack.pop())

            stack.pop()

            while stack and stack[-1].isdigit():
                num.appendleft(stack.pop())

            stack.append(int(''.join(num)) * ''.join(letters))

        return "".join(stack)