PermutationsII47.java

public class Solution {
    private ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
    private HashMap hm = new HashMap();
    public List<List<Integer>> permuteUnique(int[] nums) {
        ArrayList<Integer> set = new ArrayList<Integer>();
        boolean [] vis = new boolean[nums.length];
        helper(nums,set,vis);
        return (List) res;
    }
    
    public void helper(int[] nums, ArrayList<Integer> set, boolean[] visited){
          
         if(set.size()==nums.length){
             ArrayList a = new ArrayList<Integer>(set);
             if(hm.get(a)==null){
                 hm.put(a,1);
                 res.add(a);
             }
             return;
         }
         
         for(int i=0;i<nums.length;i++){
             if(visited[i]==false){
                 set.add(nums[i]);
                 visited[i]=true;
                 helper(nums, set, visited);
                 set.remove(set.size()-1);
                 visited[i]=false;
             }
         }
    }
}