Encode and Decode Strings: A Simple Messaging System

This challenge focuses on designing a simple encoding and decoding system for strings. Imagine you're building a basic messaging application where you need to obscure the content of messages for privacy, but in a reversible way. Your task is to implement functions for encoding and decoding strings using a specific, defined algorithm.

Problem Description

You are tasked with creating two functions: encode(string) and decode(string). The encoding process should transform a given string into a modified string, and the decoding process should reverse this transformation to recover the original string.

The encoding algorithm works as follows:

1. Iterate through the input string character by character.
2. For each character, convert it to its ASCII value.
3. Add 1 to the ASCII value.
4. Convert the new ASCII value back to a character.
5. Append this modified character to the encoded string.

The decoding algorithm is the reverse of the encoding algorithm:

1. Iterate through the encoded string character by character.
2. For each character, convert it to its ASCII value.
3. Subtract 1 from the ASCII value.
4. Convert the new ASCII value back to a character.
5. Append this modified character to the decoded string.

Key Requirements:

• The functions must handle all ASCII characters (0-127).
• The encoding and decoding processes must be reversible; decoding the encoded string should result in the original string.
• The functions should be efficient for reasonably sized strings.

Expected Behavior:

• encode("hello") should return a string representing the encoded version of "hello".
• decode("encoded_string") should return the original string that was encoded.

Edge Cases to Consider:

• Empty strings: Both encoding and decoding should handle empty strings gracefully (returning an empty string).
• Strings containing special characters (e.g., spaces, punctuation).
• Strings with characters near the ASCII boundaries (0 and 127). Consider what happens if subtracting 1 from ASCII 0 or adding 1 to ASCII 127 results in an invalid character. The behavior in these cases should be consistent.

Examples

Example 1:

Input: "hello"
Output: "ifmmp"
Explanation: 'h' (104) becomes 'i' (105), 'e' (101) becomes 'f' (102), 'l' (108) becomes 'm' (109), 'l' (108) becomes 'm' (109), 'o' (111) becomes 'p' (112).

Example 2:

Input: "ifmmp"
Output: "hello"
Explanation: 'i' (105) becomes 'h' (104), 'f' (102) becomes 'e' (101), 'm' (109) becomes 'l' (108), 'm' (109) becomes 'l' (108), 'p' (112) becomes 'o' (111).

Example 3:

Input: ""
Output: ""
Explanation: An empty string remains an empty string after encoding and decoding.

Constraints

• String Length: The input strings will have a maximum length of 1000 characters.
• Character Set: The input strings will contain only ASCII characters (values 0-127).
• Performance: The encoding and decoding functions should complete within 0.1 seconds for strings of maximum length.
• Error Handling: No explicit error handling is required. Assume the input will always be a valid string containing only ASCII characters.

Notes

• Consider using built-in functions for character-to-ASCII and ASCII-to-character conversions in your chosen language.
• The core of the challenge lies in correctly implementing the iterative encoding and decoding logic.
• Think about how to handle the edge cases where adding 1 or subtracting 1 from an ASCII value might result in a character outside the standard ASCII range. The problem description implies consistent behavior in these cases, but you should be aware of the potential issue. For example, if ASCII 0 has 1 added, it becomes ASCII 1. If ASCII 127 has 1 subtracted, it becomes ASCII 126.