[189]Rotate Array

Rotate an array of n elements to the right by k steps.

For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].

Note: Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.

[show hint]

Related problem: Reverse Words in a String II

Code

Python

Solution1:

class Solution(object):
    def rotate(self, nums, k):
        if k == None or k <= 0:
            return
        k, end = k % len(nums), len(nums) - 1
        self.reverse(nums, 0, end - k)
        self.reverse(nums, end - k + 1, end)
        self.reverse(nums, 0, end)

    def reverse(self, nums, start, end):
        while start < end:
            nums[start], nums[end] = nums[end], nums[start]
            start, end = start + 1, end - 1

Solution2:

class Solution(object):
    def rotate(self, nums, k):
        n = len(nums)
        k = k % n
        nums[:] = nums[n-k:] + nums[:n-k]

Runtime: 162ms