Encode And Decode

Problem statement

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.

Please implement encode and decode

For example:

Input: ["lint","code","love","you"] 
Output: ["lint","code","love","you"]
Explanation: One possible encode method is: "lint:;code:;love:;you"

Input: ["we", "say", ":", "yes"]
Output: ["we", "say", ":", "yes"]
Explanation:
One possible encode method is: "we:;say:;:::;yes"

Solution

The idea is to have a separator, lets say # and a length of processed word:

For example

["this", "is", "cool##"]

"4#this2#is6#cool##" # decoded

With the number we know exactly what to process.

Similar to second round in: https://www.notion.so/auspham/Amazon-Grad-2021-01e838493e124920a1214d1d8f1bf9c9?pvs=4

import unittest
from typing import *


class App:
    DELIMETER = "#"

    def encode(self, words: List[str]) -> str:
        result = []

        for word in words:
            result.append("{}#{}".format(len(word), word))

        return "".join(result)
        
    def decode(self, encoded: str) -> List[str]:
        result = []

        i = 0
        length = 0

        while i < len(encoded):

            while (encoded[i] != App.DELIMETER):
                length *= 10
                length += int(encoded[i])
                i += 1
            
            i += 1 # Skip letter #
            result.append(encoded[i: i + length])

            i += length
            length = 0
        
        return result
            

class AppTest(unittest.TestCase):
    def setUp(self):
        self.app = App()
        return super().setUp()

    def test_encode_decode(self):
        inputArray = ["we", "say", ":", "yes"]
        actual = self.app.decode(self.app.encode(inputArray))
        self.assertListEqual(inputArray, actual)

    def test_encode_decode_2(self):
        inputArray = ["lint","code","love","you"] 
        actual = self.app.decode(self.app.encode(inputArray))
        self.assertListEqual(inputArray, actual)

    def test_encode_decode_3(self):
        inputArray = [] 
        actual = self.app.decode(self.app.encode(inputArray))
        self.assertListEqual(inputArray, actual)

    def test_encode_decode_4(self):
        inputArray = ["hi"] 
        actual = self.app.decode(self.app.encode(inputArray))
        self.assertListEqual(inputArray, actual)

    def test_encode_decode_5(self):
        inputArray = ["#", "#", "#"] 
        actual = self.app.decode(self.app.encode(inputArray))
        self.assertListEqual(inputArray, actual)
    
    def test_encode_decode_6(self):
        inputArray = ["thisisaverylongwordofcourse", "is", "cool"]
        actual = self.app.decode(self.app.encode(inputArray))
        self.assertListEqual(inputArray, actual)

if __name__ == "__main__":
    unittest.main()