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.

Idea:

1. find the length of the number where the nth digit is from
2. find the actual number where the nth digit is from
3. find the nth digit and return

class Solution {
    public int findNthDigit(int n) {
        long d=9;
        int len=1,start=1;
        while(n>d*len){
            n-=d*len;
            d*=10;
            len++;
            start*=10;
        }

        int actual = start+(n-1)/len;

        String s = Integer.toString(actual);
        char c = s.charAt((n-1)%len);
        return c-'0';

    }
}