https://www.luogu.com.cn/problem/P1706
这道题也可以用STL中
next_permutation函数
关于next_permutation函数的文章 https://blog.csdn.net/qian2213762498/article/details/79683905?spm=1001.2101.3001.6650.2&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-2.pc_relevant_antiscanv2&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7ERate-2.pc_relevant_antiscanv2&utm_relevant_index=5
该函数头文件为#include<algorithm>

简要介绍一下next_permutation函数的功能

next_permutation()函数功能是输出所有比当前排列大的排列，顺序是从小到大。当排列已经是最大，返回假，否则真。

#include <iostream>
#include <algorithm>
using namespace std;
int main() {
  int a[10];
  int n;
  cin >> n;
  for(int i = 1;  i<= n; i++) {
    a[i] = i;
  }
  do {
    for(int i = 1; i <= n; i++) {
    cout << "    " <<a[i];
  }
    cout << endl; 
  }while(next_permutation(a + 1, a + n + 1));
  return 0;
}

dfs深搜

#include<iostream>

using namespace std;

const int N = 15;

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

void dfs(int u)
{
    if(u > n)
    {
        for(int i = 1; i <= n; i ++)
        printf("%5d", a[i]);
        puts("");
        return;
    }

    for(int i = 1; i <= n; i ++)
    {   
        if(!st[i])
        {
            a[u] = i;
            st[i] = true;
            dfs(u + 1);
            a[u] = 0;
            st[i] = false;
        }
    }
}



int main()
{
    cin >> n;

    dfs(1);

    return 0;
}