46-permutations.js

/*
Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Example 1:
Input: nums = [1,2,3]
Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Example 2:
Input: nums = [0,1]
Output: [[0,1],[1,0]]

Example 3:
Input: nums = [1]
Output: [[1]]
*/
/**
 * @param {number[]} nums
 * @return {number[][]}
 */
var permute = function (nums) {
  if (nums.length === 0) return [[]];
  const firstEl = nums[0];
  const rest = nums.slice(1);

  const permsWithoutFirst = permute(rest);
  const allPermutations = [];

  permsWithoutFirst.forEach((perm) => {
    for (let i = 0; i <= perm.length; i++) {
      const permsWithFirst = [...perm.slice(0, i), firstEl, ...perm.slice(i)];
      allPermutations.push(permsWithFirst);
    }
  });

  return allPermutations;
};
const result = permute([1, 2, 3]);
console.log(result);