49. lineEncoding

Task

Given a string, return its encoding defined as follows:

• First, the string is divided into the least possible number of disjoint substrings consisting of identical characters
  • for example, "aabbbc" is divided into ["aa", "bbb", "c"]
• Next, each substring with length greater than one is replaced with a concatenation of its length and the repeating character
  • for example, substring "bbb" is replaced by "3b"
• Finally, all the new strings are concatenated together in the same order and a new string is returned.

Example

For s = "aabbbc", the output should be
lineEncoding(s) = "2a3bc".

Input/Output

• [execution time limit]
  4 seconds (py3)

• [input] string s
  String consisting of lowercase English letters. Guaranteed constraints: 4 ≤ s.length ≤ 15.

• [output] string
  Encoded version of s.

My Solution

def lineEncoding(s):
    s = s + '_'
    encoded = ''
    count = 1
    for i in range(len(s) - 1):
        if s[i] == s[i + 1]:
            count += 1
        else:
            if count == 1:
                encoded += s[i]
            else:
                encoded += str(count) + s[i]
            count = 1
    return encoded