Problem

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

public class Codec {    // Encodes a list of strings to a single string.    public String encode(List
    
      strs) {        StringBuilder sb = new StringBuilder();        for (String str: strs) {            sb.append(str + "\n");        }        return sb.toString();    }    // Decodes a single string to a list of strings.    public List
     
       decode(String s) {        List
      
        strs = new ArrayList<>();        int pre = 0, i = 0;        while (i < s.length()) {            if (s.charAt(i) == '\n') {                strs.add(s.substring(pre, i));                pre = i+1;                i = i+1;            } else i++;        }        return strs;    }}