189-rotate_array.js

/**
 * Given an array, rotate the array to the right by k steps, where k is non-negative.
 * Input: nums [1,2,3,4,5,6,7], k = 3
 * Output: [5,6,7,1,2,3,4]
 * Explanation:
 * rotate 1 steps to the right: [7,1,2,3,4,5,6]
 * rotate 2 steps to the right: [6,7,1,2,3,4,5]
 * rotate 3 steps to the right: [5,6,7,1,2,3,4]
 */

/**
 *
 * @param {number[]} nums
 * @param {number} k
 * @return {void} Do not return anything, modify nums in-place instead.
 */
/*
Approach: Using Reverse
Time complexity: O(n) . n elements are reversed a total of three times.
Space complexity: O(1) . No extra space is used
*/
const revNums = (nums, start, end) => {
  while (start < end) {
    [nums[start], nums[end]] = [nums[end], nums[start]];
    start++;
    end--;
  }
};

var rotate = function (nums, k) {
  k = k % nums.length;

  nums.reverse();
  revNums(nums, 0, k - 1);
  revNums(nums, k, nums.length - 1);
  console.log(nums);
};

rotate([1, 2, 3, 4, 5, 6, 7], 3);