[LeetCode] Subsets II

Subsets II

Given a collection of integers that might contain duplicates, nums, 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 nums = 

[1,2,2]

,
a solution is:

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

解题思路：

去重的话用一个set来记录。枚举的话，可以二进制递增来枚举。i从0递增到2^n-1，若i的二进制表示中，相应位为1，则添加到项中。

class Solution {
public:
vector<vector<int>> subsetsWithDup(vector<int>& nums) {
vector<vector<int>> result;
set<vector<int>> contains; //已经包含的
std::sort(nums.begin(), nums.end());

int num = 1 << nums.size();
for(int i=0; i<num; i++){
int flag = i;
int j=0;
vector<int> item;
while(flag!=0){
if(flag&0x1==1){
item.push_back(nums[j]);
}
flag = flag>>1;
j++;
}
if(contains.find(item)==contains.end()){
contains.insert(item);
result.push_back(item);
}
}

return result;
}
};