Rotate Array — LeetCode 189 Python Solution

The problem

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

Example

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]

Python solution

class Solution:
    def rotate(self, nums: List[int], k: int) -> None:
        def reverse(i: int, j: int):
            while i < j:
                nums[i], nums[j] = nums[j], nums[i]
                i, j = i + 1, j - 1

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

Complexity

Pattern: Two Pointers

Use the order already in the input to discard half the search space at every step. LeetCode 189. Rotate Array is filed here because LeetCode tags it Two Pointers, which is the vocabulary this hub collects.

The two pointers guide has the Python template for the pattern and the 201 LeetCode problems that use it.

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