#include <iostream>
#include <cmath>
#include <vector>

using namespace std;
//排列-递归
//从k到m子序列排列
void perm(vector<int> & v,int k,int m)
{
    if (k==m)
    {
        for (int i = 0; i <= m; i++)
        {
            cout << v[i] << " ";
        }
        cout << endl;
    }
    else
    {
        for (int i = k; i <= m; i++)
        {
            swap(v[k], v[i]);
            perm(v,k+1, m);
            swap(v[k], v[i]);
        }
    }
}
int main()
{
    vector<int> v = { 1,2,3 };
    perm(v, 0, 2);//全排列

    cout << "hello world" << endl;
    return 0;
}