Sword finger offer 17 Print from 1 to maximum n digits

Original link ： The finger of the sword Offer 17. Print from 1 To the biggest n digit

solution:

        dfs, Consider large numbers

class Solution {
public:
    vector<int> res;
    string path;
    vector<int> printNumbers(int n) {
        dfs(n);
        return res;
    }

    void dfs(int n) {
        if(path.size() == n) {
            int num = stoi(path);
            if(num) res.push_back(num); //num It's not equal to 0 Just save 
            return;
        }

        for(int i = 0;i < 10;i++) {
            path.push_back(i + '0');
            dfs(n);
            path.pop_back();
        }
    }
};