LeetCode-Subsets II

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题目：https://oj.leetcode.com/problems/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],  []]

分析：采用二进制法，使用Set去重

源码：Java版本
算法分析：二进制法，时间复杂度O(2^n)，空间复杂度O(1)

public class Solution {    public List<List<Integer>> subsetsWithDup(int[] num) {        Arrays.sort(num);                  Set<List<Integer>> results = new HashSet<List<Integer>>();         List<List<Integer>> realResults = new ArrayList<List<Integer>>();                 int len=num.length;          for(int i=0;i<(1<<len);i++) {              List<Integer> path = new ArrayList<Integer>();              for(int j=0;j<len;j++) {                  if(((1<<j)&i)!=0) {                      path.add(num[j]);                  }              }              results.add(path);          }          realResults.addAll(results);        return realResults;      }    }

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