leetcode: Subsets & Subsets II
时间：2014-05-02 16:39:15
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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: vector<vector<int> > subsets(vector<int> &S) { sort(S.begin(),S.end()); vector<int> buf; vector<vector<int> > res; subset(S,0,buf,res); return res; } private: void subset(vector<int> &S, int start, vector<int> &buf, vector<vector<int> > &res) { if(start == S.size()) { res.push_back(buf); return; } subset(S,start+1,buf,res); buf.push_back(S[start]); subset(S,start+1,buf,res); buf.pop_back(); } };
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: vector<vector<int> > subsetsWithDup(vector<int> &S) { sort(S.begin(),S.end()); vector<int> buf; vector<vector<int> > res; subset(S,0,buf,res); //res.push_back(vector<int> {}); return res; } private: void subset(vector<int> &S, int start, vector<int> &buf, vector<vector<int> > &res) { if(start == S.size()) { res.push_back(buf); return; } int nextStart = distance(S.begin(),upper_bound (S.begin()+start, S.end(), S[start])); for(int i=0;i<(nextStart-start);i++) { buf.push_back(S[start]); } for(int i=(nextStart-start);i>0;i--) { subset(S,nextStart,buf,res); buf.pop_back(); } subset(S,nextStart,buf,res); } };
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