Encode and Decode Strings -- LeetCode

Posted 2020-08-04 Coder and Writer

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:

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

Machine 2 (receiver) has the function:

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

So Machine 1 does:

string encoded_string = encode(strs);

and Machine 2 does:

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.

Note:

• The string may contain any possible characters out of 256 valid ascii characters. Your algorithm should be generalized enough to work on any possible characters.
• Do not use class member/global/static variables to store states. Your encode and decode algorithms should be stateless.
• Do not rely on any library method such as eval or serialize methods. You should implement your own encode/decode algorithm.

思路：每个字符串之前添加它的长度和一个%字符。

 1 class Codec {
 2 public:
 3 
 4     // Encodes a list of strings to a single string.
 5     string encode(vector<string>& strs) {
 6         string res;
 7         for (int i = 0; i < strs.size(); i++)
 8             res += std::to_string(strs[i].size()) + "%" + strs[i];
 9         return res;
10     }
11 
12     // Decodes a single string to a list of strings.
13     vector<string> decode(string s) {
14         vector<string> res;
15         int curInd = 0;
16         int mark = s.find("%");
17         while (mark != std::string::npos) {
18             int len = std::stoi(s.substr(curInd, mark - curInd));
19             if (len) res.push_back(s.substr(mark + 1, len));
20             //in case it is an empty string
21             else res.push_back("");
22             curInd = mark + len + 1;
23             mark = s.find("%", curInd);
24         }
25         return res;
26     }
27 };
28 
29 // Your Codec object will be instantiated and called as such:
30 // Codec codec;
31 // codec.decode(codec.encode(strs));