Nth Digit

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 < 231).

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.

Tags

• Mathematics

Thought

Reference: http://bookshadow.com/weblog/2016/09/18/leetcode-nth-digit/

Code

class Solution(object):
    def findNthDigit(self, n):
        """
        :type n: int
        :rtype: int
        """
        for i in range(9):
            d = 9 * 10 ** i
            if n <= d * (i + 1): break
            n -= d * (i + 1)
        n -= 1
        return int(str(10**i + n / (i + 1))[n % (i + 1)])