题目：

题解：

class Solution:
    def combine(self, n: int, k: int) -> List[List[int]]:
        ans = []
        path = []
        
        def dfs(x):
            remain = k - len(path)
            if not remain:
                ans.append(list(path))
                return
            if n + 1 - x > remain:
                dfs(x + 1)
            path.append(x)
            dfs(x + 1)
            path.pop()
        
        dfs(1)
        return ans