You are given two integers, n and k. Your task is to return all possible combinations of k numbers chosen from the range [1, n].

The result can be returned in any order.

Note: Combinations are unordered, i.e., [1, 2] and [2, 1] are considered the same combination.

Constraints:

• $1 \leq$ n $\leq 20$

• $1 \leq$ k $\leq n$

The algorithm uses a backtracking strategy to generate all possible combinations of size $k$ from the range $[1 … n]$ ...