(LeetCode) 189. Rotate Array

Rotate Array

• Explore : Interview > Top Interveiw Questions > Easy Collection
• 분류 : Array
• 난이도 : Medium

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]

Constraints

• 1 <= nums.length <= 2 * 10^4
• -2^31 <= nums[i] <= 2^31 - 1
• 0 <= k <= 10^5

Solution (Not supported in LeetCode)

Exapnder

class Solution {
    fun rotate(nums: IntArray, k: Int): Unit {
        nums.reverse(nums.size - k, nums.size)
        nums.reverse(0, nums.size - k)
        nums.reverse()
    }
}

Solution

Exapnder

class Solution {
    fun rotate(nums: IntArray, k: Int): Unit {
        for (i in 0 until k) {
            var index = nums.size - 1
            var temp = nums[index]
            for (j in index downTo 1) {
                nums[j] = nums[j - 1]
            }
            nums[0] = temp
        }
    }
}

Point of Thinking

• K를 기준으로 reverse를 3번하면 된다.
  • LeetCode에서는 IntArray.reverse()를 지원하지않는다..
• 결국 2중 for loop로 풀었다.