77. Combinations

s1.py

class Solution:
    def combine(self, n: int, k: int) -> List[List[int]]:
        def dfs(nums: List[int], path: List[int]):
            if len(path) == k:
                res.append(path)
                return

            for i in range(len(nums)):
                dfs(
                    nums[i+1:],
                    path + [nums[i]]
                )
            
        res = []
        dfs([i + 1 for i in range(n)], [])
        
        return res

s2.py

class Solution:
    def combine(self, n: int, k: int) -> List[List[int]]:
        return list(itertools.combinations(range(1, n + 1), k))