leetcode-Subsets II

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],
  []
]

class Solution {
public:
    void sub(vector<int> &a, vector<int> set, vector<vector<int> > &sets, int n, int i, bool t)
    {
        if(n == i)
        {
            sets.push_back(set);
            return;
        }
        
        if((t == true)&&(a[i] == a[i-1]))
        {
            set.push_back(a[i]);
            sub(a,set,sets,n,i+1,true);
            return;
        }
        else
        {
            sub(a,set,sets,n,i+1,false);
            set.push_back(a[i]);
            sub(a,set,sets,n,i+1,true);
            return;
        }
    }
    
    vector<vector<int> > subsetsWithDup(vector<int> &S) {
        vector<int> a = S;
        sort(a.begin(),a.end());
        vector<int>set;
        vector<vector<int> > sets;
        int n = a.size();
        int num = 0;
        sub(a,set,sets,n,num,false);
        return sets;
    }
};