Encode and Decode Strings

Encode and Decode Strings is a Medium Data Structures and Algorithms interview problem you can solve, run and submit on Thita.ai. It belongs to the Design Patterns pattern, in the Design (General/Specific) subpattern.

Problem statement

You are given a list of strings strs, where each string may contain any of the 256 valid ASCII characters (including special characters and empty strings). Your task is to implement two methods:

- encode(strs): Encodes the list of strings into a single string. - decode(s): Decodes the single string back into the original list of strings.

The encoded string produced by encode must contain all the information necessary to reconstruct the original list exactly, even if some strings are empty or contain special characters. You are not allowed to use any built-in serialization methods (such as eval).

Constraints: - 1 <= strs.length <= 200 - 0 <= strs[i].length <= 200 - Each strs[i] may contain any ASCII character.

Return the encoded string from encode, and the decoded list of strings from decode.

Topics and companies

Topics: Array, String, Design.

Reported in interviews at Microsoft.

How to practise Encode and Decode Strings on Thita.ai

Starter code is provided in C#, C++, Go, Java, JavaScript and Python. Your solution runs against 5 test cases for this problem, with the AI coach available for a hint when you are stuck rather than a finished answer. The reference solution runs in O(N), where N is the total number of characters in all strings. Both encoding and decoding iterate through all characters once. time and O(N), where N is the total number of characters in all strings. The encoded string and the decoded vector both require space proportional to the input. space.

Open Encode and Decode Strings in the code editor, or read the Encode and Decode Strings editorial for a worked solution with its approach and complexity analysis.

Where Encode and Decode Strings sits in the DSA pattern sheet

• Design Patterns pattern guide
• Design (General/Specific) subpattern
• The full DSA patterns sheet
• All coding practice problems

Problems related to Encode and Decode Strings

Other problems that use the same Design (General/Specific) and Design Patterns techniques:

• All O`one Data Structure — Hard, same subpattern
• Design a Stack With Increment Operation — Medium, same subpattern
• Design a Text Editor — Hard, same subpattern
• Design Circular Deque — Medium, same subpattern
• Design Circular Queue — Medium, same subpattern
• Design Compressed String Iterator — Easy, same subpattern