2025-08-02 18:22:51 +0300 MSK

class Solution:
    def maximum69Number(self, num: int) -> int:
        digits = []
        while num > 0:
            digits.append(num % 10)
            num //= 10
        digits.reverse()
        res = 0
        enc = False
        length = len(digits)
        for i, digit in enumerate(digits):
            if digit == 6 and not enc:
                digit = 9
                enc = True
            res += (10 ** (length - i - 1)) * digit
        return res