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经典的回溯法
class Solution {
public:
vector<vector<int>> subsets(vector<int>& nums) {
vector<vector<int>> result;
if(nums.empty()) return result;
vector<int> list;
dfs(0, result,list,nums);
return result;
}
private:
void dfs(int pos, vector<vector<int>>& result, vector<int>& list, vector<int>& nums){
result.push_back(list);
for(int i = pos; i < nums.size(); i++){
list.push_back(nums[i]);
dfs(i+1, result, list, nums);
list.pop_back();
}
}
};
