400. Nth Digit （找第n个数字）

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.

public class Solution {
public int findNthDigit(int n) {
int len = 1;
long num = 9, start = 0;
while (n > num*len) {
n -= len * num;
start+=num;
len++;
num *= 10;
}
int res;
if(n%len==0){
res = (""+(start+n/len)).charAt(len-1)-'0';
}else{
res = (""+(start+n/len+1)).charAt(n%len-1)-'0';
}
return res;
}
}