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.

分析：

count + "#"

public class Solution {

    public String[] decode(String str) {
        ArrayList<String> list = new ArrayList<String>();
        int pointer = 0;
        while (pointer < str.length()) {
            int end = pointer;
            while (str.charAt(end) != '#') {
                end++;
            }
            int count = Integer.parseInt(str.substring(pointer, end));
            list.add(str.substring(end + 1, end + 1 + count));
            pointer = end + 1 + count;
        }
        return list.toArray(new String[list.size()]);
    }

    public String encode(String[] strs) {
        StringBuilder sb = new StringBuilder();
        for (String s : strs) {
            sb.append(s.length());
            sb.append("#");
            sb.append(s);
        }
        return sb.toString();
    }
}