Leetcode 189. Rotate Array



Leetcode Top Interview 150 的其中一題

題目描述

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

範例

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 <= 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?

解法

方法:檢查每個數字現在是否等於 val,是的話改成 100001,這樣排序後就會在最後面,不在列入檢查的陣列前面

func rotate(nums []int, k int)  {
    k = k % len(nums)

    new := make([]int, 0)
    for i:= len(nums) - k; i<len(nums); i++ {
        new = append(new, nums[i])
    }

    for i:=0; i<len(nums)-k; i++ {
        new = append(new, nums[i])
    }

    copy(nums, new)
}

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