LeetCode in Kotlin

189. Rotate Array

Medium

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]

Constraints:

• 1 <= nums.length <= 105
• -231 <= nums[i] <= 231 - 1
• 0 <= k <= 105

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

@Suppress("NAME_SHADOWING")
class Solution {
    private fun reverse(nums: IntArray, l: Int, r: Int) {
        var l = l
        var r = r
        while (l <= r) {
            val temp = nums[l]
            nums[l] = nums[r]
            nums[r] = temp
            l++
            r--
        }
    }

    fun rotate(nums: IntArray, k: Int) {
        val n = nums.size
        val t = n - k % n
        reverse(nums, 0, t - 1)
        reverse(nums, t, n - 1)
        reverse(nums, 0, n - 1)
    }
}

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