LeetCode OJ

这道题的做法，一定得掌握啊！！！  elegant & beautiful & concise

下面是AC代码：

 /**
      * Given a set of distinct integers, S, return all possible subsets.
      * 这道题的做法应该要记住！！！！！
      * @param s
      * @return
      */
     public ArrayList<ArrayList<Integer>> subsets(int[] s){
         ArrayList<ArrayList<Integer>> r = new  ArrayList<ArrayList<Integer>>();
         Arrays.sort(s);
         ArrayList<Integer> sub = new ArrayList<Integer>();
         r.add(sub);
         for(int e : s){
             int cur_size = r.size();
             for(int j=0;j<cur_size;j++){
                 sub = new ArrayList<Integer>();
                 sub.addAll(r.get(j));
                 sub.add(e);
                 r.add(sub);
             }
         }
         return r;
     }
     /**
      * Given a collection of integers that might contain duplicates, S, return all possible subsets.
      * @param num
      * @return
      */
     public ArrayList<ArrayList<Integer>> subsetsWithDup(int[] num) {
         ArrayList<ArrayList<Integer>> r = new ArrayList<ArrayList<Integer>>();
         Arrays.sort(num);
         int last = Integer.MAX_VALUE;
         int mark = 0;
         ArrayList<Integer> sub = new ArrayList<Integer>();
         r.add(sub);
         for(int e:num){
             int cur_size = r.size();
             int begin = e==last? mark:0;
             for(int i = begin;i<cur_size;i++){
                 sub = new ArrayList<Integer>();
                 sub.addAll(r.get(i));
                 sub.add(e);
                 r.add(sub);
             }
             last = e;
             mark = cur_size;
         }
         return r;
     }