<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:
    def dfs(self, cur: int, prev: int, stack: str) -> None:
        if cur == len(self.nums):
            if stack.count("_") >= 2:
                self.ans.add(stack)
        else:
            # 1. select current number
            if prev <= self.nums[cur]:
                s = stack+"_"+str(self.nums[cur])
                self.dfs(cur+1, self.nums[cur], s)
            # 2. not select current number
            self.dfs(cur+1, prev, stack)
    
    def findSubsequences(self, nums: List[int]) -> List[List[int]]:
        self.nums = nums
        self.ans = set()
        self.dfs(0, -1000, "")
        
        res = []
        for s in self.ans:
            strs = s.split("_")
            l = []
            for ss in strs:
                if ss == "":
                    continue
                else:
                    l.append(int(ss))
            res.append(l)
        
        return res
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