Subsets II @LeetCode

package Level4;  
  
import java.util.ArrayList;  
import java.util.Arrays;  
import java.util.HashSet;  
import java.util.Set;  
  
/** 
 * Subsets II  
 *  
 *  Given a collection of integers that might contain duplicates, S, return all possible subsets. 

Note: 
Elements in a subset must be in non-descending order. 
The solution set must not contain duplicate subsets. 
For example, 
If S = [1,2,2], a solution is: 

[ 
  [2], 
  [1], 
  [1,2,2], 
  [2,2], 
  [1,2], 
  [] 
] 
 * 
 */  
public class S90 {  
  
    public static void main(String[] args) {  
        int[] num = {1,2,2};  
        System.out.println(subsetsWithDup(num));  
    }  
  
    // 与之前相比改用HashSet来过滤  
    public static ArrayList





> subsetsWithDup(int[] num) {  
        int len = num.length;  
        Set> set = new HashSet>();  
        Arrays.sort(num);  
          
        // 利用2进制对应的bit来求所有subset，2进制中，0代表不选，1代表选择  
        for(int i=0; i list = new ArrayList();  
            int tmp = i;  
            // 对长为len的数，循环检查最右位是否为一  
            for(int j=0; j>= 1;  
                if(bit == 1){  
                    list.add(num[j]);  
                }  
            }  
            set.add(list);  
        }  
        return new ArrayList>(set);  
    }  
  
}