Encode and Decode Strings

class Codec {
public:
    string serialize(vector<string>& inputStrings) {
        string result;
        for (string &element : inputStrings) {
            result += to_string(element.size()) + "/:" + element;
        }
        return result;
    }

    vector<string> deserialize(string data) {
        vector<string> output;
        size_t startPos = 0;
        while (startPos < data.size()) {
            size_t delimiter = data.find("/:", startPos);
            int len = stoi(data.substr(startPos, delimiter - startPos));
            string extracted = data.substr(delimiter + 2, len);
            output.push_back(extracted);
            startPos = delimiter + 2 + len;
        }
        return output;
    }
};

In this guide, you will explore how to encode and decode strings using C++ programming. The provided solution is implemented within a Codec class comprising two main functions: serialize and deserialize.

• Focus first on the serialize function:

  • Begin by initializing an empty string result.
  • Iterate through every string in the input vector inputStrings.
  • For each string, append its length, followed by the delimiter "/:" and the string itself, to result.
  • Return the concatenated result, which now holds the encoded form of all input strings.

• Next, examine the deserialize function:

  • Start by initializing an empty vector of strings output.
  • Use a startPos to track the current position in the encoded string data.
  • Use a while loop to process data until startPos reaches the end of the string.
  • Locate the delimiter "/:" from startPos to find where the current string's length definition ends.
  • Extract the length of the string and use it to get the actual string value from data.
  • Place the extracted string into the output vector and adjust startPos for the next iteration.
  • Once the loop completes, return output, which contains all the decoded strings.

This solution effectively handles the encoding and decoding of an array of strings through the use of length and delimiter, ensuring string boundaries are maintained irrespective of content. The implementation is both straightforward and efficient, utilizing standard string and vector operations in C++.

public class Codec {
    public String serialize(List<String> inputList) {
        StringBuilder result = new StringBuilder();
        for (String element : inputList) {
            result.append(element.length()).append("/:").append(element);
        }
        return result.toString();
    }

    public List<String> deserialize(String encoded) {
        List<String> resultArray = new ArrayList<>();
        int position = 0;
        while (position < encoded.length()) {
            int marker = encoded.indexOf("/:", position);
            int size = Integer.parseInt(encoded.substring(position, marker));
            String segment = encoded.substring(marker + 2, marker + 2 + size);
            resultArray.add(segment);
            position = marker + 2 + size;
        }
        return resultArray;
    }
}

The solution presented in Java provides mechanisms to both encode and decode lists of strings efficiently using a custom serialization format. Follow the techniques below to understand how each part functions:

• Encoding Process:

  1. Instantiate a StringBuilder to store the serialized output.
  2. Loop through each string in the input list.
  3. For each string, append its length and a special separator "/:" to the StringBuilder. Follow this by appending the string itself.
  4. Convert the StringBuilder to a string before returning it, which represents the encoded form of the input list.

• Decoding Process:

  1. Create an empty ArrayList<String> to hold the decoded strings.
  2. Initialize a position variable to track the current index within the encoded string.
  3. Use a while loop to process the encoded string until the end is reached.
  4. Inside the loop, identify the next occurrence of the separator "/:" to determine the end of the current length segment.
  5. Extract the length of the next string using Integer.parseInt() and determine the exact substring representing the string using the identified length.
  6. Add the extracted string to the list resultArray.
  7. Adjust position to move past the current string and continue the process.

The solution effectively handles the encoding and decoding of strings, avoiding common issues such as the interference of special characters within the strings themselves by encoding the length explicitly. This method ensures that each string is accurately retrieved during the decoding process regardless of the string content.

class StringCodec:
    def encode(self, strings):
        # Prepare an encoded string
        encoded_result = ''
        for item in strings:
            # Join string length, delimiter, and the string
            encoded_result += str(len(item)) + '/:' + item
        return encoded_result

    def decode(self, encoded_value):
        # List to keep decoded strings
        decoded_list = []
        idx = 0
        while idx < len(encoded_value):
            # Locate the delimiter
            delimiter_position = encoded_value.find('/:', idx)
            # Extract the substring length
            str_length = int(encoded_value[idx:delimiter_position])
            # Extract the actual string
            extracted_str = encoded_value[delimiter_position+2 : delimiter_position+2+str_length]
            # Append the extracted string to list
            decoded_list.append(extracted_str)
            # Update index to move to the next string part
            idx = delimiter_position + 2 + str_length
        return decoded_list

The provided Python code defines a class StringCodec with methods to encode and decode lists of strings. Here's a breakdown of its functionality:

• Encoding:

  • The encode method takes a list of strings and processes each string to form an encoded string. Each string is encoded by prefixing it with its length followed by the special delimiter '/:', and then appending the actual string itself.
  • For example, encoding ['hello', 'world!'] results in '5/:hello6/:world!'.

• Decoding:

  • The decode method reverses this process. It takes an encoded string as input and decodes it back into the original list of strings.
  • It iterates over the encoded string, locating the delimiter to determine where one encoded part ends and next begins, extracting both the length of each string and the string itself.
  • Using this information, it reconstructs and appends each string to a list, which contains the decoded strings after the loop completes.

For practical usage:

• Initialize an instance of StringCodec.
• Use encode() to convert a list of strings into a single encoded string.
• Use decode() with an encoded string to get back the original list of strings. This allows for efficient storage and transmission of string data, particularly useful in scenarios where string manipulation and custom storage formats are required.