# https://leetcode.com/problems/string-compression-iii

class Solution:
    def compressedString(self, word: str) -> str:
        last_char = None
        l = 0
        result = []
        def to_string(ch, cnt, result):
            if cnt <= 9:
                result.append(str(cnt))
                result.append(ch)
            else:
                cnt -= 9
                result.append('9')
                result.append(ch)
                to_string(ch, cnt, result)
        for ch in word:
            if last_char == None:
                last_char = ch
                l = 1
                continue
            if last_char != ch:
                to_string(last_char, l, result)
                l = 1
                last_char = ch
            else:
                l += 1
        to_string(last_char, l, result)
        return ''.join(result)