271. 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;}

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) { ???????string res; ???????for(auto str:strs) res+=to_string(str.size())+"@"+str; ???????return res; ???} ???// Decodes a single string to a list of strings. ???vector<string> decode(string s) { ???????vector<string>res; ???????int head = 0; ???????while(head<s.size()) ???????{ ???????????int pos = s.find("@",head); ???????????int len = stoll(s.substr(head,pos-head)); ???????????string str = s.substr(pos+1,len); ???????????res.push_back(str); ???????????head = pos+1+len; ???????} ???????return res; ???}};// Your Codec object will be instantiated and called as such:// Codec codec;// codec.decode(codec.encode(strs));