<p>Given an integer array <code>nums</code>, return <em>all the different possible non-decreasing subsequences of the given array with at least two elements</em>. You may return the answer in <strong>any order</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [4,6,7,7]
<strong>Output:</strong> [[4,6],[4,6,7],[4,6,7,7],[4,7],[4,7,7],[6,7],[6,7,7],[7,7]]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [4,4,3,2,1]
<strong>Output:</strong> [[4,4]]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 15</code></li>
	<li><code>-100 &lt;= nums[i] &lt;= 100</code></li>
</ul>

class Solution {
    private:
    void solve (vector<int> &nums,int n, vector<int> list,set<vector<int>> &ans, int idx){
        if (idx>=n){
            if (list.size()>=2){
                ans.insert(list);
            }
            return;
        }
        //choose
        if (list.empty() || nums[idx]>= list.back()){
        list.push_back(nums[idx]);
        solve (nums,n,list,ans,idx+1);
        list.pop_back();
        }

        //not choose
        if(list.empty()|| nums[idx]!= list.back()){
        solve (nums,n,list,ans,idx+1);
        }
    }
public:
    vector<vector<int>> findSubsequences(vector<int>& nums) {
        vector<vector<int>> res;
        vector<int> list;
        int n= nums.size();
        set<vector<int>> ans;
        solve (nums,n,list,ans,0);
        for (auto it: ans){
            res.push_back(it);
        }
        return res;
    }
};
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