java实现全排列

public class Test2 {
    @Test
    public void test(){
        int[] arr = {2,3,1};
        List<String> list = permute(arr);
        System.out.println(list);
        System.out.println(Arrays.toString(arr));
    }

    private List<String> permute(int[] arr) {
        return permute0(arr,0,new ArrayList<>());
    }
    private List<String> permute0(int[] arr,int now,List<String> rs) {
        if(now == arr.length) {
            rs.add(Arrays.toString(arr));
        }
        for (int i = now; i < arr.length; i++) {
            swap(arr,now,i);
            permute0(arr,now+1,rs);
            swap(arr,now,i);
        }
        return rs;
    }
    private void swap(int[] arr,int i,int j) {
        int t = arr[i];
        arr[i] = arr[j];
        arr[j] = t;
    }
}