String Compression III(LeetCode 3163):

Problem

Given a string word, compress it using the following algorithm:

  • Begin with an empty string comp. While word is not empty, use the following operation:
    • Remove a maximum length prefix of word made of a single character c repeating at most 9 times.
    • Append the length of the prefix followed by c to comp.

Return the string comp.

 

Example 1:

Input: word = "abcde"

Output: "1a1b1c1d1e"

Explanation:

Initially, comp = "". Apply the operation 5 times, choosing "a", "b", "c", "d", and "e" as the prefix in each operation.

For each prefix, append "1" followed by the character to comp.

Example 2:

Input: word = "aaaaaaaaaaaaaabb"

Output: "9a5a2b"

Explanation:

Initially, comp = "". Apply the operation 3 times, choosing "aaaaaaaaa", "aaaaa", and "bb" as the prefix in each operation.

  • For prefix "aaaaaaaaa", append "9" followed by "a" to comp.
  • For prefix "aaaaa", append "5" followed by "a" to comp.
  • For prefix "bb", append "2" followed by "b" to comp.

 

Constraints:

  • 1 <= word.length <= 2 * 105
  • word consists only of lowercase English letters.