271. 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.

Solution

(1) Java

(2) Python

class Codec:

    def encode(self, strs):
        """Encodes a list of strings to a single string.

        :type strs: List[str]
        :rtype: str
        """
        rst = ""
        for string in strs:
            rst = rst+"#"+str(len(string))+"#"+string
        return rst

    def decode(self, s):
        """Decodes a single string to a list of strings.

        :type s: str
        :rtype: List[str]
        """
        rst = []
        if not s or s[0] != "#":
            return rst
        while s:
            s = s[1:]
            idx = s.find("#")
            length = int(s[:idx])
            string = s[idx+1:idx+1+length]
            rst.append(string)
            s = s[idx+1+length:]
        return rst


# Your Codec object will be instantiated and called as such:
# codec = Codec()
# codec.decode(codec.encode(strs))

(3) Scala