def main(tasks: str) -> str: stack: list = [] decoded_string = '' actual_number = 0 for symbol in tasks: if symbol.isdigit(): actual_number = actual_number * 10 + int(symbol) elif symbol == '[': stack.append((decoded_string, actual_number)) decoded_string = '' actual_number = 0 elif symbol == ']': prev_str, prev_num = stack.pop() decoded_string = prev_str + prev_num * decoded_string else: decoded_string += symbol return decoded_string

The given code defines a function main that takes a string tasks as input and decodes it using a stack-based approach. The function iterates through each character in the input string and performs decoding based on the rules specified in the task.

Here's a breakdown of the code:

1. Initialize an empty stack and variables decoded_string and actual_number to store the decoded string and the actual number respectively.
2. Iterate through each character in the input string tasks.
3. If the character is a digit, update the actual_number by multiplying it by 10 and adding the integer value of the digit.
4. If the character is '[', push the current decoded_string and actual_number onto the stack, reset decoded_string and actual_number.
5. If the character is ']', pop the previous decoded_string and actual_number from the stack, and update decoded_string by concatenating the previous string prev_str prev_num times.
6. For any other character, simply append it to the decoded_string.
7. Finally, return the fully decoded string.

You can call this function with a string containing encoded tasks to get the decoded result.