Subsets and Subsets II (回溯，DFS，组合问题)

[1,2,3]

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

该题和Combinations很类似，只不过是k需要从0到size中取值。

classSolution{
private:
vector<vector<int>>res;
vector<int>s;
public:
voidtra(intk,intstart,intdep,vector<int>temp)
{
if(dep==k){
res.push_back(temp);
return;
}
for(inti=start;i<s.size();++i){
temp.push_back(s[i]);
tra(k,i+1,dep+1,temp);//是i+1，而不是start+1
temp.erase(temp.end()-1);
}
}
vector<vector<int>>subsets(vector<int>&S){
s=S;
sort(s.begin(),s.end());
vector<int>temp;
for(intk=0;k<=s.size();++k){
tra(k,0,0,temp);
}
returnres;
}
};

Subsets2

[1,2,2]

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

classSolution{
private:
vector<vector<int>>res;
vector<int>s;
public:
voidtra(intk,intstart,intdep,vector<int>temp)
{
if(dep==k){
for(inti=0;i<res.size();++i)
{
if(res[i]==temp)return;
}
res.push_back(temp);
return;
}
for(inti=start;i<s.size();++i){
temp.push_back(s[i]);
tra(k,i+1,dep+1,temp);
temp.erase(temp.end()-1);
}
}
vector<vector<int>>subsetsWithDup(vector<int>&S){
s=S;
sort(s.begin(),s.end());
vector<int>temp;
res.push_back(temp);
for(intk=1;k<=s.size();++k){
tra(k,0,0,temp);
}
returnres;
}
};