把数字翻译成字符串-动态规划(剑指offer 46)-python

python

class Solution:
    def translateNum(self, num: int):
        num = str(num)
        n = len(num)
        if n == 1:
            return 1

        dp = [0] * n
        dp[0] = 1
        dp[1] = 2 if int(num[0]+num[1]) <= 25 else 1

        for i in range(2, n):
            if num[i-1] != '0' and int(num[i-1]+num[i]) <= 25:
                dp[i] = dp[i-1] + dp[i-2]
            else:
                dp[i] = dp[i-1]
        
        return dp[-1]