em……这玩意其实就是……返回结果再输出

#include <iostream>
#include <vector>

using namespace std;

vector<vector<int>> com(vector<int> &v)
{
    vector<vector<int>> res;
    if (v.size() == 1)
    {
        res.push_back(v);
        return res;
    }
    for (int i = 0; i < v.size(); i ++)
    {
        int tmp = v[i];
        v.erase(v.begin() + i, v.begin() + i + 1);
        auto c = com(v);
        v.insert(v.begin() + i, tmp);
        for (auto p : c)
        {
            vector<int> t;
            t.push_back(v[i]);
            for (int x : p) t.push_back(x);
            res.push_back(t);
        }
    }
    return res;
}

int main()
{
    int n; cin >> n;
    vector<int> t;
    for (int i = 1; i <= n; i ++) t.push_back(i);
    auto res = com(t);
    for (auto v : res)
    {
        for (auto x : v) cout << x << ' ';
        cout << "\n";
    }
    return 0;
}

现在我写的：

#include <iostream>

using namespace std;

const int N = 11;

int n;
int a[N];
bool st[N];

void dfs(int u)
{
    if (u >= n)
    {
        for (int i = 0; i < n; i ++ ) cout << a[i] << ' ';
        puts("");
        return ;
    }

    for (int i = 1; i <= n; i ++ )
        if (!st[i])
        {
            st[i] = true, a[u] = i;
            dfs(u + 1);
            st[i] = false;
        }
}

int main()
{
    cin >> n;

    dfs(0);

    return 0;
}