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 str string字符串 * @return string字符串vector */ vector<string> Permutation(string str) { // write code here vector<string> res; set<string> existsstr; int n = str.size(); backtrace(res, existsstr,0,n,str); ...