dfs

#include <iostream>

using namespace std;

const int N = 10;//一共有0-9个数

int n;

void dfs(int u,int nums[],bool st[])//u代表层数
{
    if(u > n)//枚举到最后一层
    {
        for (int i = 0; i <= n;i ++)
            cout << nums[i] << ' ';
        cout << endl;
    }
    else
    {
        for (int i = 1; i <= n;i ++)//按照字典序遍历数字
        {
            if(!st[i])
            {
                st[i] = true;//标记已经存了数字
                nums[u] = i;//存入数字
                dfs(u + 1, nums, st);//进入下一层
                st[i] = false;//恢复现场
            }
        }
    }
}

int main()
{
    cin >> n;

    int nums[N];
    bool st[N] = {0};

    dfs(1, nums, st);
}

next_permutation函数

#include<bits/stdc++.h>

using namespace std;

const int N = 10;
int a[N];
int n;

int main()
{
    cin >> n;
    for (int i = 0; i < n; i ++)
        a[i] = i + 1;

    for (int i = 0; i < n; i++)
        cout << a[i] << ' ';

    cout << endl;

    while(next_permutation(a,a+n))
    {
        for (int i = 0; i < n; i++)
            cout << a[i] << ' ';
        cout << endl;
    }
}