STL的全排列函数
next_permutation(a + 1, a + 1 + n)；

#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
#define inf 0x3f3f3f3f
int a[100];
int main()
{
    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 + 1 + n));
}

输入：
4
这是输出：
1 2 3 4
1 2 4 3
1 3 2 4
1 3 4 2
1 4 2 3
1 4 3 2
2 1 3 4
2 1 4 3
2 3 1 4
2 3 4 1
2 4 1 3
2 4 3 1
3 1 2 4
3 1 4 2
3 2 1 4
3 2 4 1
3 4 1 2
3 4 2 1
4 1 2 3
4 1 3 2
4 2 1 3
4 2 3 1
4 3 1 2
4 3 2 1