Given a collection of numbers that might contain duplicates, return all possible unique permutations.
For example,[1,1,2] have the following unique permutations:[1,1,2], [1,2,1], and [2,1,1].
class Solution {
public:
void DFS(vector<vector<int> > &res,vector<int> &ans,vector<bool> &flag,vector<int> &num)
{
if(ans.size()==num.size())
{
res.push_back(ans);
return;
}
for(int i=0;i<num.size();i++)
{
if(i&&num[i]==num[i-1]&&!flag[i-1]) continue;
if(!flag[i])
{
ans.push_back(num[i]);
flag[i]=true;
DFS(res,ans,flag,num);
flag[i]=false;
ans.pop_back();
}
}
}
vector<vector<int> > permuteUnique(vector<int> &num) {
sort(num.begin(),num.end());//先排序
vector<vector<int> > res;
vector<bool> flag(num.size(),false);
vector<int> ans;
DFS(res,ans,flag,num);
return res;
}
};