<p>Given two integers <code>n</code> and <code>k</code>, return <em>all possible combinations of</em> <code>k</code> <em>numbers chosen from the range</em> <code>[1, n]</code>.</p>

<p>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> n = 4, k = 2
<strong>Output:</strong> [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]
<strong>Explanation:</strong> There are 4 choose 2 = 6 total combinations.
Note that combinations are unordered, i.e., [1,2] and [2,1] are considered to be the same combination.
</pre>

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

<pre>
<strong>Input:</strong> n = 1, k = 1
<strong>Output:</strong> [[1]]
<strong>Explanation:</strong> There is 1 choose 1 = 1 total combination.
</pre>

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

<ul>
	<li><code>1 &lt;= n &lt;= 20</code></li>
	<li><code>1 &lt;= k &lt;= n</code></li>
</ul>

class Solution:
    def get_combines(self,arr,n,k,num,elem,start):
        if num==k:
            return [[elem]]
        if start>=n:
            return []
        combines=[]
        for i in range(start,n):
            res=self.get_combines(arr,n,k,num+1,arr[i],i+1)
            for r in res:
                combines.append([elem]+r)
        return combines

    def combine(self, n: int, k: int) -> List[List[int]]:
        arr=[i for i in range(1,n+1)]
        ans=[]
        for i in range(n):
            res=self.get_combines(arr,n,k,1,arr[i],i+1)
            ans.extend(res)
        return ans



        
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