[LeetCode] Strobogrammatic Number II

This problem can be solved easily once you find the regularities :-) This link has done it for you. You may refer to its Python version. I rewrite it in C++ below.

class Solution {
public:
    vector<string> findStrobogrammatic(int n) { 
        vector<string> strobos;
        if (n & 1) strobos = {"0", "1", "8"};
        else strobos = {""};
        vector<string> bases = {"00", "11", "88", "69", "96"};
        int m = bases.size(); 
        while (n > 1) {
            n -= 2;
            vector<string> temp;
            for (string strobo : strobos)
                for (int i = (n < 2 ? 1 : 0); i < m; i++)
                    temp.push_back(bases[i].substr(0, 1) + strobo + bases[i].substr(1));
            swap(temp, strobos);
        }
        return strobos;
    }
};