[刷题]leetcode189

三次反转

1.整体反转

2.前半部分反转

3.后半部分反转

tips：python库函数list.reverse()会报错，需要自己实现。

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        """
        Do not return anything, modify nums in-place instead.
        """

        def reverse(nums, i, j):
            while i <= j:
                nums[i], nums[j] = nums[j], nums[i]
                i += 1
                j -= 1


        n = len(nums)
        k = k%n
        reverse(nums,0,n-1)
        reverse(nums,0,k-1)
        reverse(nums,k,n-1)