class Codec {

// 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());

res.push_back('.');

res += str;

}

return res;

}

// Decodes a single string to a list of strings.

vector<string> decode(string s) {

vector<string> res;

auto it = s.begin();

while (it != s.end()) {

int str_size = 0;

string tmp = "";

while (*it != '.') {

str_size = str_size * 10 + (*it - '0');

it++;

}

it++;

for (int i = 0; i < str_size; i++) {

tmp.push_back(*it);

it++;

}

res.push_back(tmp);

}

return res;

}

};