C++简单代码/set去重/剪枝/追溯法/10行：

C++简单代码/set去重/剪枝/追溯法/10行：

class Solution {
public:
    set<string> res; //去重
    vector<string> Permutation(string str) {
        if (str.empty()) return {};
        string s;
        cutdown (str, s);
        return vector<string> (res.begin(), res.end());
    }
    void cutdown(string str, string s) {
        if (str.size() == 0) res.insert(s);
        for (int i = 0; i < str.size(); i ++) {
            string temp = str;
            cutdown(temp.erase(i, 1), s + str[i]);
        }
    }
};