【LeetCode】Subsets II

题目描述：

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],  []]

递归解。将当前子集向后添上s[i]后向下递归。

先将给定的S排序后再递归，若s[i]==s[i-1]则添上s[i]后的子集与添上s[i-1]生成的子集是重复的，只需添加一个就好了。

代码如下：

class Solution {public:vector<vector<int> > subsetsWithDup(vector<int> &S) {std::sort(S.begin(), S.end());vector<vector<int>> res;getSubsets(res, S, 0, vector<int>());return res;}void getSubsets(vector<vector<int>> &res, vector<int> &s, int index, vector<int> subset){res.push_back(subset);for (int i = index; i < s.size(); i++){if (i != index && s[i] == s[i - 1])continue;subset.push_back(s[i]);getSubsets(res, s, i + 1, subset);subset.pop_back();}}};