46 数字翻译成字符串

class Solution():
    def num2str(self,num):
        n = len(str(num))
        f = [0]*(n+1)
        f[n] = 1
        f[n-1] = 1
        for i in range(n-2,-1,-1):
            f[i] = f[i+1]+self.check(str(num)[i],str(num)[i+1])*f[i+2]
        return f[0]

    def check(self,a,b):
        checknum = int(str(a)+str(b))
        if (checknum >= 10) & (checknum<= 25):
            return 1
        else:
            return 0


s = Solution()
print(s.num2str(2526))