LeetCode 0400 - Nth Digit

Input:
3

Output:
3

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.

class Solution {
public:
    int findNthDigit(int n) {
        long long start = 1;
        long long len = 1;
        long long count = 9;
        while(n > len * count) {
            n -= len * count;
            len++;
            count *= 10;
            start *= 10;
        }
        return std::to_string(start + (n - 1) / len)[(n - 1) % len] - '0';
    }
};