可以算是dfs梦开始的地方了

import java.util.*;

public class Main {
    static int n;
    static int N = 10;
    static int[] nums = new int[N];
    static boolean[] st = new boolean[N];

    private static void dfs(int u, int[] nums, boolean st[]) {
        if (u == n) {
            for (int i = 0; i < n; i++) System.out.print(nums[i] + " ");
            System.out.println();
        } else {
            for (int i = 1; i <= n; i++) {
                if (!st[i]) {
                    st[i] = true;
                    nums[u] = i;
                    dfs(u + 1, nums, st);
                    st[i] = false;
                }
            }
        }
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();

        dfs(0, nums, st);
    }
}