31&&47

#include<vector>
#include<algorithm>
#include<iostream>
using namespace std;

 void nextPermutation(vector<int>& nums) {
        if(nums.size()<2)return ;
        int i;
        for(i=nums.size()-2;i>=0;--i){
            if(nums[i]<nums[i+1])break;
        }
        if(i>=0){
            int k=i;
            for(i=nums.size()-1;i>k;--i){
                if(nums[i]>nums[k])break;
            }
            swap(nums[k],nums[i]);
            reverse(nums.begin()+k+1,nums.end());
            
        }else reverse(nums.begin(),nums.end());
    }

    vector<vector<int>> permuteUnique(vector<int>& nums) {
        if(nums.empty())return vector<vector<int>>{};
        vector<vector<int>>ret;
        vector<int>tmp;
        vector<bool> used(nums.size(),false);
        sort(nums.begin(),nums.end());
        helper(ret,nums,tmp,used);
        return ret;
    }

    void helper(vector<vector<int>>&ret,vector<int>&nums,vector<int>&tmp,vector<bool> used){
        if(tmp.size()==nums.size()){
            ret.push_back(tmp);
            return ;
        }
        for(int i=0;i<nums.size();++i){
            if(used[i])continue;
            if(i>0&&used[i-1]==false&&nums[i-1]==nums[i])continue;
            used[i]=true;
            tmp.push_back(nums[i]);
            helper(ret,nums,tmp,used);
            used[i]=false;
            tmp.pop_back();
        }
    }
int main(){
	vector<int>v{1,2,4,6,5,3,2,1};
	nextPermutation(v);
	for(auto i: v)cout<<i<<",";
	cout<<endl;
	return 0;
}