public class Solution {    public List
     
      
       > permute(int[] nums) {        List
       
        
         > ret=new ArrayList
         
          
           >(); permute(new ArrayList
           
            (),ret,nums); return ret; } private void permute(List
            
              list,List
             
              
               > ret, int[] nums){ if(list.size()==nums.length) ret.add(new ArrayList
               
                (list)); else for(int i=0;i