Subsets
Given a set of distinctintegers, 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 ofintegers 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);
}
};
leetcode: Subsets & Subsets II,布布扣,bubuko.com