求给定字符串的所有非空字串，且子串不重复

给定字符串"www.baidu.com" ，求所有不重复的非空子串，C++代码如下：

#include <iostream>
#include <set>
#include <vector>
#include <sstream>
#include <iterator>
#include <algorithm>

using namespace std;

void get_substrs(const string &str,set<string> &substrs)
{
        vector<string> vec;
        int i;
        for (i = 0; i < str.size(); i++) {
                vec.clear();
                copy(substrs.begin(),substrs.end(),back_inserter(vec));
                vector<string>::iterator itr;
                for (itr = vec.begin(); itr != vec.end(); itr++) {
                        substrs.insert(*itr + str[i]);
                }
                stringstream stream;
                stream << str[i];
                substrs.insert(stream.str());
        }
}
int main() {
        set<string> substrs;
        get_substrs("www.baidu.com",substrs);
        set<string>::iterator itr;
        for (itr = substrs.begin(); itr != substrs.end(); itr++) {
                cout << *itr << endl;
        }
        cout << "=====total " << substrs.size() << " records=====" << endl;
        return 0;
}