from typing import List

class Solution:

# Special character used as delimiter between length and actual string

delimiter = "$"

def encode(self, strs: List[str]) -> str:

"""

Encodes a list of strings into a single string.

Format: [length]$[string][length]$[string]...

"""

encoded = []

# Encode each word using the format: length + delimiter + word

for word in strs:

# Convert word length to string, add delimiter, then add the word itself

encoded.append(f"{len(word)}{self.delimiter}{word}")

# Join all encoded elements into a single string and return

return "".join(encoded)

def decode(self, encoded: str) -> List[str]:

"""

Decodes a single string back to the original list of strings.

"""

decoded = [] # List to store the decoded strings

current_index = 0 # Pointer to track current position in the encoded string

# Process the encoded string until we reach the end

while current_index < len(encoded):

# Starting from current_index, find the position of delimiter

delimiter_index = current_index

# Move forward until we find the delimiter character

while encoded[delimiter_index] != self.delimiter:

delimiter_index += 1

# Extract and convert the length prefix to integer

word_length = int(encoded[current_index:delimiter_index])

# Calculate the start position of the word (after the delimiter)

word_start = delimiter_index + 1

# Calculate the end position of the word

word_end = word_start + word_length

# Extract the word using the calculated positions

word = encoded[word_start:word_end]

# Add the decoded word to our result list

decoded.append(word)

# Move the current index to the end of this word for the next iteration

current_index = word_end

return decoded