Permutations
Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.
permute([1, 2, 3]);
// [
// [1, 2, 3],
// [1, 3, 2],
// [2, 1, 3],
// [2, 3, 1],
// [3, 1, 2],
// [3, 2, 1]
// ]