Python 代码

class Solution(object):
    def digitAtIndex(self, n):
        i = 1; s = 9
        while n > s * i:
            n -= s * i
            s *= 10
            i += 1
        res = 10 ** (i - 1) + n / i - 1
        if n % i == 0:
            res = str(res)[-1] 
        else:
            res = str(res + 1)[n % i - 1]
        return res