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. Show Company Tags Show Tags

Solution

public class Solution {
    public int findNthDigit(int n) {
        if(n <= 0) return -1;

        long count = 9;
        int startN = 1;
        int bitPerNum = 1;

        while(n > count * bitPerNum) {
            n -= count * bitPerNum;
            startN += count;
            count *= 10;
            bitPerNum ++;
        }

        int the = startN + (n - 1) / bitPerNum;
        for(int i = 0; i < (  (bitPerNum-1) -  ((n-1) % bitPerNum) ); i++) the /= 10;
        return the %= 10;
    }
}