Encode or Decode Message

Encodes or decodes a message using a shared numeric key. Input

• Operation:
• 1 = Encode
• 2 = Decode
• Message (string)
• Key (positive integer) Encoding (Operation 1) Duplicates each character based on the corresponding digit in the key. Example: Message: Open, Key: 123 → Output: Oppeen Decoding (Operation 2) Compresses repeated characters based on digits in the key. Example: Message: Oppeen, Key: 123 → Output: Open Rules Apply digits in key cyclically or until message ends. Remaining characters (if key ends first) are left unchanged. Return -1 for invalid input or mismatched patterns during decoding.

Example 1

Input:

operation = 1
message = "Open"
key = 123

Output:

"Oppeen"

Explanation: ~~

Example 2

Input:

operation = 2
message = "Oppeen"
key = 123

Output:

"Open"

Explanation: