# Leetcode 77 - Combinations

Given two integers n and k, return all possible combinations of k numbers out of the range [1, n].

You may return the answer in any order.

Example 1:

Input: n = 4, k = 2
Output:
[
[2,4],
[3,4],
[2,3],
[1,2],
[1,3],
[1,4],
]
Note: One of the most typical backtracking problems. Remeber to use spread operator while pushing element into ans because we are passing path as reference. path always points to a place in memory and this variable will eventually be empty because of our undo operations in code. So if we don’t use spread operator to clone a new array and push it into ans, what we get will just be empty.