Nth Natural Number

Given a positive integer N. You have to find Nth natural number after removing all the numbers containing digit 9.

• Time : O(log₉N)
• Space : O(log₉N)

class Solution{
public:
    long long findNth(long long N){
        string s = "";
        while(N) {
            s.push_back(N % 9 | 0b110000);
            N /= 9;
        }
        reverse(begin(s), end(s));
        return stol(s);
    }
};