题目：

题解：

class Solution {
public:
    int findNthDigit(int n) {
        int d = 1, count = 9;
        while (n > (long) d * count) {
            n -= d * count;
            d++;
            count *= 10;
        }
        int index = n - 1;
        int start = (int) pow(10, d - 1);
        int num = start + index / d;
        int digitIndex = index % d;
        int digit = (num / (int) (pow(10, d - digitIndex - 1))) % 10;
        return digit;
    }
};