<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 {
    // - prashu

    // - bit manipulation approach
public:
    vector<vector<int>> findSubsequences(vector<int>& nums) {
        set<vector<int>> uniqueSubsequences;
        int n = nums.size();
        for(int i=3;i<pow(2,n);i++) {
            if(ceil(log2(i))==log2(i)) continue;
            int last = -101;
            bool isValidSubsequence = true;
            vector<int> subsequence;
            for(int b=0;b<n;b++) {
                if(i&(1<<b)) {
                    if(nums[b]>=last) {
                        subsequence.push_back(nums[b]);
                        last = nums[b];
                    } else {
                        isValidSubsequence = false;
                        break;
                    }
                }
            }
            if(isValidSubsequence) {
                uniqueSubsequences.insert(subsequence);
            }
        }
        vector<vector<int>> res(uniqueSubsequences.begin(), uniqueSubsequences.end());
        return res;
    }
};
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