leetcode-90. Subsets II

90. Subsets II

Given a collection of integers that might contain duplicates, nums, return all possible subsets (the power set).
Note: The solution set must not contain duplicate subsets.
For example,

If nums = 

[1,2,2]

, a solution
is:

[
[2],
[1],
[1,2,2],
[2,2],
[1,2],
[]
]

和上一题Subsets不同的就是这个集合里的元素是可以重复的。
在第一题的基础上，排序过后，相同的元素都是相邻的，只要过滤掉相同的即可

class Solution {
public List<List<Integer>> subsetsWithDup(int[] nums) {
List<List<Integer>> list = new ArrayList<>();
Arrays.sort(nums);
backtrack(list, new ArrayList<>(), nums, 0);
return list;
}

private void backtrack(List<List<Integer>> list, List<Integer> tempList, int [] nums, int start){
list.add(new ArrayList<>(tempList));
for(int i = start; i < nums.length; i++){
if(i > start && nums[i] == nums[i-1]) continue; // skip duplicates
tempList.add(nums[i]);
backtrack(list, tempList, nums, i + 1);
tempList.remove(tempList.size() - 1);
}
}
}

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还是不理解，，埋个坑，以后填