[LeetCode] Encode and Decode Strings

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.app

Machine 1 (sender) has the function:less

string encode(vector<string> strs) {
  // ... your code
  return encoded_string;
}

Machine 2 (receiver) has the function:ui

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

So Machine 1 does:code

string encoded_string = encode(strs);

and Machine 2 does:ci

vector<string> strs2 = decode(encoded_string);

strs2 in Machine 2 should be the same as strs in Machine 1.string

Implement the encode and decode methods.it

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.io

Solution

public class Codec {

    // Encodes a list of strings to a single string.
    public String encode(List<String> 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<String> decode(String s) {
        List<String> 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;
    }
}
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