271. Encode and Decode Strings

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271. Encode and Decode Strings

Description

Design an algorithm to encode a list of strings to a string. The encoded string is then sent over the network and is decoded back to the original list of strings.

Machine 1 (sender) has the function:

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string encode(vector<string> strs) {
  // ... your code
  return encoded_string;
}

Machine 2 (receiver) has the function:

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vector<string> decode(string s) {
  //... your code
  return strs;
}

So Machine 1 does:

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string encoded_string = encode(strs);

and Machine 2 does:

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vector<string> strs2 = decode(encoded_string);

strs2 in Machine 2 should be the same as strs in Machine 1.

Implement the encode and decode methods.

You are not allowed tosolve the problem using any serialize methods (such as eval).

Example 1:

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Input: dummy_input = ["Hello","World"]
Output: ["Hello","World"]
Explanation:
Machine 1:
Codec encoder = new Codec();
String msg = encoder.encode(strs);
Machine 1 ---msg---> Machine 2

Machine 2:
Codec decoder = new Codec();
String[] strs = decoder.decode(msg);

Example 2:

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Input: dummy_input = [""]
Output: [""]

Constraints:

  • 1 <= strs.length <= 200
  • 0 <= strs[i].length <= 200
  • strs[i] contains any possible characters out of 256 valid ASCII characters.

Follow up: Could you write a generalized algorithm to work on any possible set of characters?

Hints/Notes

  • 2025/01/04
  • string
  • premium

Solution

Language: C++

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class Codec {
public:

    // Encodes a list of strings to a single string.
    string encode(vector<string>& strs) {
        string res;
        for (auto& str : strs) {
            int n = str.size();
            res += to_string(n);
            res.push_back(' ');
            res += str;
            res.push_back(' ');
        }
        return res;
    }

    // Decodes a single string to a list of strings.
    vector<string> decode(string s) {
        vector<string> res;
        for (int i = 0; i < s.size(); ) {
            int start = i;
            while (s[i] != ' ') {
                i++;
            }
            int size = stoi(s.substr(start, i - start));
            i++;
            res.push_back(s.substr(i, size));
            i += size + 1;
        }
        return res;
    }
};

// Your Codec object will be instantiated and called as such:
// Codec codec;
// codec.decode(codec.encode(strs));