Encode and Decode Strings

Medium

Problem Statement

Design an algorithm to encode a list of strings to a single string. The encoded string is then decoded back to the original list of strings.

Please implement encode and decode

Example 1:

Input: ["neet","code","love","you"]

Output:["neet","code","love","you"]

Example 2:

Input: ["we","say",":","yes"]

Output: ["we","say",":","yes"]

Constraints:

0 <= strs.length < 100
0 <= strs[i].length < 200
strs[i] contains only UTF-8 characters.

Recommended Time & Space Complexity

You should aim for a solution with O(m) time for each encode() and decode() call and O(m+n) space, where m is the sum of lengths of all the strings and n is the number of strings.

Hint 1

A naive solution would be to use a non-ascii character as a delimiter. Can you think of a better way?

Hint 2

Try to encode and decode the strings using a smart approach based on the lengths of each string. How can you differentiate between the lengths and any numbers that might be present in the strings?

Hint 3

We can use an encoding approach where we start with a number representing the length of the string, followed by a separator character (let's use # for simplicity), and then the string itself. To decode, we read the number until we reach a #, then use that number to read the specified number of characters as the string.

Examples

1Example 1

Input:

{
  "strs": []
}

Output:

""

2Example 2

Input:

{
  "strs": [
    "hello"
  ]
}

Output:

"5#hello"

3Example 3

Input:

{
  "strs": [
    "a",
    "b"
  ]
}

Output:

"1#a1#b"