leetcode[78]Subsets

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

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

class Solution {
public:
void subset(vector<vector<int>> &res,vector<int> &temp,vector<int> &S, int from)
{
    res.push_back(temp);
    for(int i=from;i<S.size();i++)
    {
//        if(i>from&&S[i]==S[i-1])continue;
        temp.push_back(S[i]);
        subset(res,temp,S,i+1);
        temp.pop_back();
    }
}
vector<vector<int> > subsets(vector<int> &S) {
    vector<vector<int>> res;
    res.clear();
    vector<int> temp;
    temp.clear();
    int n=S.size();
    if(n<1)return res;
    sort(S.begin(),S.end());
    subset(res,temp,S,0);
    return res;
}
/*
void subset(vector<vector<int>> &res,vector<int> &temp,vector<int> &S,int from)
{
    if(from==S.size())
    {
        res.push_back(temp);
        return;
    }
    temp.push_back(S[from]);
    subset(res,temp,S,from+1);
    temp.pop_back();
    subset(res,temp,S,from+1);
}
    vector<vector<int> > subsets(vector<int> &S) {
        vector<vector<int>> res;
        res.clear();
        vector<int> temp;
        temp.clear();
        int n=S.size();
        if(n<1)return res;
        sort(S.begin(),S.end());
        subset(res,temp,S,0);
        return res;
    }
void subset(vector<vector<int>> &res,vector<int> &temp,vector<int> &S,int from, int to,int k)
{
    if(k==0)
    {
        res.push_back(temp);
        return;
    }
    else
    {
        if(from>to)return;
        else
        {
            temp.push_back(S[from]);
            subset(res,temp,S,from+1,to,k-1);
            temp.pop_back();
            subset(res,temp,S,from+1,to,k);
            return;
        }
    }
}
    vector<vector<int> > subsets(vector<int> &S) {
        vector<vector<int>> res;
        res.clear();
        vector<int> temp;
        temp.clear();
        int n=S.size();
        sort(S.begin(),S.end());
        if(n<1)return res;
        for(int k=0;k<=n;k++)
        {
            subset(res,temp,S,0,n-1,k);
        }
        return res;
    }
*/
};