[LeetCode] Subsets II

[Problem]
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],
[]
]

[Solution]

class Solution {
public:
vector<vector<int> > subsets(vector<int> &S, int begin, int m){
vector<vector<int> > res;
map<int, int> dup;
if(m == 1){
for(int i = begin; i < S.size(); ++i){
// filtering duplicates
if(dup.find(S[i]) != dup.end()){
continue;
}
dup.insert(make_pair(S[i], 1));

// generate subsets
vector<int> r;
r.push_back(S[i]);
res.push_back(r);
}
}
else{
for(int i = begin; i < S.size(); ++i){
// filtering duplicates
if(dup.find(S[i]) != dup.end()){
continue;
}
dup.insert(make_pair(S[i], 1));

// generate subsets with S[i]
vector<vector<int> > r = subsets(S, i+1, m-1);
for(int j = 0; j < r.size(); ++j){
r[j].insert(r[j].begin(), S[i]);
res.push_back(r[j]);
}
}
}
return res;
}

// subsets
vector<vector<int> > subsetsWithDup(vector<int> &S) {
// Start typing your C/C++ solution below
// DO NOT write int main() function

// insert an empty set
vector<vector<int> > res;
vector<int> tmp;
res.push_back(tmp);

// sort
sort(S.begin(), S.end());

// generate subsets
for(int i = 1; i <= S.size(); ++i){
vector<vector<int> > r = subsets(S, 0, i);
for(int j = 0; j < r.size(); ++j){
res.push_back(r[j]);
}
}
return res;
}
};

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