【剑指offer】【】44. 数字序列中某一位的数字

class Solution {
public:
    int findNthDigit(int n) {
        long long i = 1, num = 9, base = 1;
        while(n > i * num)
        {
            n -= i * num;
            i ++; 
            num *= 10;
            base *= 10;
        }
        int number = base + (n + i - 1) / i - 1;
        int r = n % i ? n % i : i;
        for(int j = 0; j < i - r; j++) number /= 10;
        return number % 10;
    }
};