c++ 秒啊，不过实际不需要vector直接对string进行sort也可以

#include<iostream>
#include<vector>
#include<string>
#include<algorithm>
using namespace std;
vector<char> a;
int main()
{
    string str;
    while (cin >> str)
    {
        a.clear();
        int len = str.size();
        for (int i = 0; i < len; i++)
        {
            a.push_back(str[i]);
        }
        sort(a.begin(), a.end());
        for (vector<char>::iterator it = a.begin(); it != a.end(); it++)
        {
            cout << *it;
        }
        cout << endl;

    }
    return 0;
}