[Leetcode] subsets [31]

Topic

Given a set of distinct integers, S, return all possible subsets.

Note:

• Elements in a subset must is 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], [1,3], [+]  ,  [2,3], [up  ],  []]

Link to original topic (point me)

Thinking of solving problems

Sub-collection issues. Give a set to find out all of its subsets. This question is also a combinatorial problem-the old idea: recursive plus cycle. The understanding of such a topic is to find a practical example, and then simulate a layer of recursion, a layer of uniform, hands-on understanding 2 times, this type of problem, basically there are ideas.

Code implementation

Class Solution {public:    vector<vector<int> > Subsets (vector<int> &s) {        vector< vector<int> > ret;        Sort (S.begin (), S.end ());        Helper (0, S, vector<int> (), ret);        return ret;    }        void helper (int start, const vector<int>& S, vector<int> part, vector<vector<int> >& ret {        if (start = = S.size ()) return;        if (start==0) Ret.push_back (part);        for (int i=start; i<s.size (); ++i) {            part.push_back (s[i]);            Ret.push_back (part);            Helper (i+1, S, part, ret);            Part.pop_back ();}}    ;

And another very similar topic for this question, subset Ii.

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[Leetcode] subsets [31]