Leetcode 271: Encode and Decode Strings

https://leetcode.com/problems/encode-and-decode-strings/

Encode and Decode Strings

Total Accepted: 1272 Total Submissions: 4999 Difficulty: Medium

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.

 

Code:

class Codec:
    def encode(self, strs): 
        return ''.join(s.replace('|', '||') + ' | ' for s in strs) 
    def decode(self, s): 
        return [t.replace('||', '|') for t in s.split(' | ')[:-1]]

 

Idea:

Use ” | ” as a delimiter of strings. If any string has “|” in it, you need to replace it with “||” in advance. When decoding, you first get ” | ” splitted words. Then, if there is any “||” in splitted words, you need to replace it back with “|”. Don’t forget to exclude the last element of `s.split(‘ | ‘)` since it is an empty string. 

 

Reference:

https://leetcode.com/discuss/54910/1-liners-ruby-python

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