189. Rotate Array

Problem

Given an array, rotate the array to the right by k steps, where k is non-negative.

Example 1:

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]

Example 2:

Input: nums = [-1,-100,3,99], k = 2
Output: [3,99,-1,-100]
Explanation: 
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]

Constraint

• 1 <= nums.length <= 10^5
• -2^31 <= nums[i] <= 2^31 - 1
• 0 <= k <= 10^5

Follow Up

• Try to come up with as many solutions as you can. There are at least three different ways to solve this problem.
• Could you do it in-place with O(1) extra space?

Solution 1

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {void} Do not return anything, modify nums in-place instead.
 */
var rotate = function(nums, k) {
  k %= nums.length
  const reverse = (left, right) => {
    const middle = Math.floor((left + right) / 2)
    for (let i = left; i <= middle; i++) {
      const temp = nums[i]
      nums[i] = nums[right - (i - left)]
      nums[right - (i - left)] = temp
    }
  }
  reverse(0, nums.length - 1)
  reverse(0, k - 1)
  reverse(k, nums.length - 1)
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(n).