C++ 解法, 执行用时: 11ms, 内存消耗: 3200KB, 提交时间: 2022-06-07

class Solution {
public:
    void bt(string& s,int startIndex,vector<string>& r,string& temp)
    {
        r.emplace_back(temp);
        int used[26]={0};
        for(int i=startIndex;i<s.size();i++)
        {
            if(used[s[i]-'a']==1)
                continue;
            temp.push_back(s[i]);
            used[s[i]-'a']=1;
            bt(s,i+1,r,temp); 
            temp.pop_back();
        }
    }
    vector<string> generatePermutation(string s) {
        vector<string>r;
        string temp;
        bt(s,0,r,temp); 
        return r;
    }
};

C++ 解法, 执行用时: 13ms, 内存消耗: 3240KB, 提交时间: 2022-08-06

class Solution {
public:
    int n;
    void dfs(vector<string>&re,string &s,string &path,int st)
    {
        re.push_back(path);
        if(st==n){return;}
        int mp[128];
        memset(mp,0,sizeof(mp));
        
        for(int i=st;i<n;i++)
        {
            if(mp[s[i]]==0)
            {
                mp[s[i]]=1;
                path.push_back(s[i]);
                dfs(re,s,path,i+1);
                path.pop_back();
            }
        }
    }
    vector<string> generatePermutation(string s) {
        n = s.size();
        vector<string> re;
        //vector<int> visall(n);
        string path="";
        dfs(re,s,path,0);
        return re;
    }
};

C++ 解法, 执行用时: 13ms, 内存消耗: 3336KB, 提交时间: 2022-06-01

static const auto io_sync_off = [](){
    std::ios::sync_with_stdio(false);
    std::cout.tie(nullptr);
    std::cin.tie(nullptr);
    return nullptr;
}();
class Solution {
public:
    void bt(string& s,int startIndex,vector<string>& r,string& temp)
    {
        r.emplace_back(temp);
        int used[26]={0};
        for(int i=startIndex;i<s.size();i++)
        {
            if(used[s[i]-'a']==1)
                continue;
            temp.push_back(s[i]);
            used[s[i]-'a']=1;
            bt(s,i+1,r,temp); 
            temp.pop_back();
        }
    }
    vector<string> generatePermutation(string s) {
        vector<string>r;
        string temp;
        bt(s,0,r,temp); 
        return r;
    }
};

C++ 解法, 执行用时: 14ms, 内存消耗: 3308KB, 提交时间: 2022-08-03

class Solution {
  public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param s string字符串
     * @return string字符串vector
     */
    vector<string> generatePermutation(string s) {
        vector<string> ans;
        string tmp;
        helper(ans, s, 0, tmp);
        return ans;
    }

    void helper(vector<string>& ans, const string& s, const int& index,
                string tmp) {
        ans.emplace_back(tmp);
        int used[26] = {0};
        for (int i = index; i < s.size(); ++i) {
            if (used[s[i] - 'a'] == 1)
                continue;
            tmp.push_back(s[i]);
            used[s[i] - 'a'] = 1;
            helper(ans, s, i + 1, tmp);
            tmp.pop_back();
        }
    }
};

C++ 解法, 执行用时: 14ms, 内存消耗: 5392KB, 提交时间: 2022-05-17

class Solution {
public:
    vector<string> result;
    string path;
    void backtracking(string &s,int startIndex){
        result.push_back(path);
        int used[26]={0};//用数组来对本层去重
        for(int i=startIndex;i<s.size();i++){
            if(used[s[i]-'a']==1){
                continue;
            }
            path.push_back(s[i]);
            used[s[i]-'a']=1;
            backtracking(s, i+1);
            path.pop_back();
        }
    }
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param s string字符串 
     * @return string字符串vector
     */
    vector<string> generatePermutation(string s) {
        // write code here
        result.clear();
        path.clear();
        //sort(s.begin(),s.end());
        backtracking(s,0);
        return result;
    }
};