
public class Solution {
ArrayList<ArrayList<Integer>> res=new ArrayList();
public ArrayList<ArrayList<Integer>> permute(int[] num) {
LinkedList<Integer> list = new LinkedList<>();
backTrack(num,list);
}
public void backTrack(int[] num, LinkedList<Integer> list){
if(list.size()==num.length){
res.add(list);
return;
}
for(int i = 0; i < num.length; i++){
if(list.contains(num[i])){
continue;
}
list.add(num[i]);
backTrack(num,list);
list.removeLast();
}
}
}