77. Combinations - LeetCode Solution

class Solution:
    def combine(self, n: int, k: int) -> List[List[int]]:
        ans = []
        
        def trav(i, up):
            if i == n+1:
                return 
            if len(up) == k:
                ans.append(up)
                return 
            
            for j in range(i+1, n+1, 1):
                trav(j, up + [j])
        
        trav(0, [])
        return ans