LeetCode Q271: 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 strs) {
  // ... your code
  return encoded_string;
}

Machine 2 (receiver) has the function:

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

So Machine 1 does:

string encoded_string = encode(strs);

and Machine 2 does:

vector 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.

Solution:

	class Codec {
	public:
	string encode(vector<string>& strs) {
	string res;
	for(int i=0; i<strs.size(); i++){
	string str = strs[i];
	res = res + string("#") + to_string(str.length()) + string("#") + str;
	}
	return res;
	}
	// Decodes a single string to a list of strings.
	vector<string> decode(string s) {
	vector<string> res;
	if(s.length()<=2)
	return res;
	for(int i=0; i<s.length();){
	string numStr;
	i++;
	while(s[i]!='#') {
	numStr=numStr+string(1, s[i]);
	i++;
	}
	i++;
	string str;
	if(i>s.length()-1){
	res.push_back(str);
	break;
	}
	int num = numStr.length()==0? 0:stoi(numStr);
	str = s.substr(i, num);
	res.push_back(str);
	i = i+num;
	}
	return res;
	}
	};
	// Your Codec object will be instantiated and called as such:
	// Codec codec;
	// codec.decode(codec.encode(strs));

view raw Q271.cpp hosted with ❤ by GitHub