题解 | #字符串的排列#

class Solution {
public:
    vector<string> Permutation(string str) {
        vector<string> ans;
        backtracking(str, 0, ans);
        //去重复
        unordered_set<string> ansset;
        vector<string> newans;
        for(int i = 0; i < ans.size(); i++){
            ansset.insert(ans[i]);
        }
        for(auto pos = ansset.begin(); pos != ansset.end(); pos++){
            newans.push_back(*pos);
        }
        return newans;
    }

    void backtracking(string& str, int level, vector<string>& ans){
        if(level==str.length()-1){
            ans.push_back(str);
            return;
        }
        for(int i = level; i < str.length(); i++){
                swap(str[i],str[level]);
                backtracking(str, level+1, ans);
                swap(str[i],str[level]);
        }
    }

};