Question

Find the nth digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, …

Note: n is positive and will fit within the range of a 32-bit signed integer (n < 2^31).

Example 1:

Input:
3

Output:
3

Example 2:

Input:
11

Output:
0

Explanation:
The 11th digit of the sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ... is a 0, which is part of the number 10.

Solution

class Solution:
    def findNthDigit(self, n):
        """
        :type n: int
        :rtype: int
        """
        if n <= 9:
            return n

        digits = 1
        count = 9
        while n > count * digits:
            n -= count * digits
            count *= 10
            digits += 1

        num = (n - 1) // digits
        digit = (n - 1) % digits
        res = 10 ** (digits - 1)
        res += num
        return int(str(res)[digit])