[Leetcode]Encode and Decode Strings

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.

class Codec {
public:
    // Encodes a list of strings to a single string.
    string encode(vector<string> strs) {
    	if(strs.size() < 1)return "";
    	//encode string: len#string
    	string s;
    	for(int i = 0;i < strs.size();i++){
    		s.append(to_string(strs[i].size());
    		s.append("#");
    		s.append(strs[i]);
    	}
    	return s;
    }

    // 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 n = 0;
    		while(i < s.size() && s[i] != '#'){
    			n = n*10 + s[i]-'0';
    			++i;
    		}
    		res.push_back(s.substr(i+1,n));
    		i += n + 1;
    	}
    	return res;
    }
};

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