leetcode - 189. Rotate Array

Description

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

Example 1:

复制代码
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:

复制代码
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:

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

Follow up:

复制代码
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

Solved after help...

For a space o ( 1 ) o(1) o(1) solution, one straightforward way is: start with 0, use current value to set the new index, and then update the current value with the original value in the new index, and keep going until we replaced all the numbers.

This works for most cases, but doesn't work when k = k % n, for example, when n=4 and k=2, if we start with 0, then we jump to 2, then we jump back to 0. This could create a loop.

To avoid this loop, before starting, we should keep track of where we started, and once we found we arrived at start again, we increase start by 1 and keep going.

Time complexity: o ( n ) o(n) o(n)

Space complexity: o ( 1 ) o(1) o(1)

Code

python3 复制代码
class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """
        k %= len(nums)
        rotate_cnt = 0
        start = 0
        while rotate_cnt < len(nums):
            new_index, value_to_set = start, nums[start]
            while True:
                new_index = (new_index + k) % len(nums)
                ori_value = nums[new_index]
                nums[new_index] = value_to_set
                value_to_set = ori_value
                rotate_cnt += 1
                if new_index == start:
                    break
            start += 1
相关推荐
WaitWaitWait015 小时前
LeetCode每日一题4.20
算法·leetcode
蒟蒻小袁5 小时前
力扣面试150题--有效的括号和简化路径
算法·leetcode·面试
阳洞洞8 小时前
leetcode 二分查找应用
算法·leetcode·二分查找
Gerry_Liang10 小时前
LeetCode热题100——283. 移动零
数据结构·算法·leetcode
Espresso Macchiato11 小时前
Leetcode 3523. Make Array Non-decreasing
leetcode··leetcode medium·leetcode 3523·leetcode周赛446
Aqua Cheng.13 小时前
25.4.22华为--算法真题整理(2025年4月22日)
java·算法·leetcode·华为·面试
良木林14 小时前
240423 leetcode exercises
算法·leetcode
满怀101514 小时前
【LeetCode】7.整数反转
leetcode·题解
记得早睡~17 小时前
leetcode98-验证二叉搜索树
数据结构·算法·leetcode
清羽_ls19 小时前
leetcode-位运算
前端·算法·leetcode·位运算