Leetcode #78 Subsets

Given a set of distinct integers, 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 = [1,2,3], a solution is:

[  [3],  [1],  [2],  [1,2,3],  [1,3],  [2,3],  [1,2],  []]

Difficulty: Medium

void gen(vector<vector<int> >& ans,vector<int>& v,vector<int>& nums,int dep,int n,int index){        if(dep<=0||index>n-1)            return;        vector<int> v1 = v;        while(index<=n-dep)        {            v1.push_back(nums[index]);            if(dep==1)                ans.push_back(v1);            else                gen(ans,v1,nums,dep-1,n,index+1);            v1 = v;            index++;        }            }    vector<vector<int> > subsets(vector<int>& nums) {        vector<int> v;        vector<vector<int> > ans;        ans.push_back(v);        sort(nums.begin(),nums.end());        //ans.push_back(nums);        int i = 1;        int len = nums.size();        while(i<=len)        {            gen(ans,v,nums,i,len,0);            i++;        }        return ans;                    }