Rotate Array

RotateArray.swift

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

Follow up:

Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
Could you do it in-place with O(1) extra space?
 

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]
*/

class Solution {
    func rotate(_ nums: inout [Int], _ k: Int) {
        let newK = k % nums.count
        print("newK = \(newK)")
        //Reverse All
        reverse(&nums, start: 0, end: nums.count-1)
        //Reverse first K
        reverse(&nums, start: 0, end: newK-1)
        //Reverse last n-K
        reverse(&nums, start: newK, end: nums.count-1)
    }
    
    func reverse(_ nums: inout [Int], start: Int, end: Int) {
        var startInd = start
        var endInd = end
        while startInd < endInd {
            
            //Using swapAt does the job, but time taken is more compared to assignment
            //nums.swapAt(startInd, endInd)
            
            let temp = nums[startInd]
            nums[startInd] = nums[endInd]
            nums[endInd] = temp
            startInd += 1
            endInd -= 1
        }
    }
        
        
var inp = [1,2,3,4,5,6,7]
Solution().rotate(&inp, 8)
print(inp)