217. Contains Duplicate

    /*
     * 217. Contains Duplicate 
     * 2016-6-12 by Mingyang 
     * 很简单的hashset的方法
     */
     public boolean containsDuplicate(int[] nums) {
            int len=nums.length;
            if(nums==null||len==0)
              return false;
          HashSet<Integer> map=new HashSet<Integer>();
          for(int i=0;i<len;i++){
              if(map.contains(nums[i]))
                return true;
              map.add(nums[i]);
          }
          return false;
      }