Practice/OpenAI/Leetcode 271. Encode and Decode Strings

Leetcode 271. Encode and Decode Strings

CodingOptional

Problem

Create a codec (encoder/decoder) that can transform an array of strings into a single string representation and then reconstruct the original array from that representation. Your implementation must handle all possible string content, including empty strings, strings containing any Unicode characters, and strings that might contain sequences that look like delimiters or control characters.

The key challenge is that the strings in the input array can contain any characters, so you cannot simply use a delimiter like a comma or semicolon, as those characters might appear in the input strings themselves. Your encoding scheme must be lossless — decoding must always produce exactly the original array.

Requirements

1. Implement an encode method that takes a list of strings and returns a single encoded string
2. Implement a decode method that takes an encoded string and returns the original list of strings
3. The encoding must be lossless: decode(encode(strings)) must always equal strings
4. Handle all edge cases: empty strings, empty arrays, strings with any characters
5. The solution must work without maintaining any state between encode and decode calls

Constraints

• 0 <= strings.length <= 1000
• 0 <= strings[i].length <= 1000
• Each string can contain any valid Unicode characters
• Time complexity: O(n) where n is the total number of characters across all strings
• Space complexity: O(n) for the encoded output

Examples

Example 1:

Input: ["hello", "world"] Output: ["hello", "world"] Explanation: After encoding to a single string and then decoding, we get back the original array

Example 2:

Input: ["a", "", "b"] Output: ["a", "", "b"] Explanation: Empty strings must be preserved in their correct positions

Example 3:

Input: ["hello:world", "test,string", "special#chars"] Output: ["hello:world", "test,string", "special#chars"] Explanation: Common delimiter characters appearing in strings must not break the encoding

Example 4:

Input: [] Output: [] Explanation: An empty array should encode and decode to an empty array