Given a string s, encode the string such that its encoded length is the shortest.
The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k times. k should be a positive integer.
If an encoding process does not make the string shorter, then do not encode it. If there are several solutions, return any of them.
Example 1:
Input: s = "aaa" Output: "aaa" Explanation: There is no way to encode it such that it is shorter than the input string, so we do not encode it.
Example 2:
Input: s = "aaaaa" Output: "5[a]" Explanation: "5[a]" is shorter than "aaaaa" by 1 character.
Example 3:
Input: s = "aaaaaaaaaa" Output: "10[a]" Explanation: "a9[a]" or "9[a]a" are also valid solutions, both of them have the same length = 5, which is the same as "10[a]".
Constraints:
1 <= s.length <= 150sconsists of only lowercase English letters.