Is Reverse K Subarrays easy or hard?

Reverse K Subarrays is typically considered a medium-level problem. The algorithm itself is straightforward, but handling segment boundaries and index calculations correctly can cause mistakes during interviews.

Reverse K Subarrays Python/Java solution

Most implementations iterate over the array with a step size of k and reverse each segment using a two-pointer loop. Python, Java, C++, Go, TypeScript, and Rust solutions follow the same logic with small syntax differences.

How to solve Reverse K Subarrays in O(n)?

Traverse the array in increments of k. For each starting index, set two pointers at the beginning and end of the k-sized segment, then swap elements while moving the pointers inward. Each element participates in at most one reversal operation, which keeps the total work linear.

What is the best approach for Reverse K Subarrays?

The in-place two-pointer approach is the best solution. Iterate through the array in steps of k and reverse each segment using two pointers from both ends of the segment. This method runs in O(n) time and uses O(1) extra space, making it optimal for interviews and large inputs.

Is Reverse K Subarrays asked at Google/Amazon/Meta?

Array segment manipulation problems appear frequently in interviews at companies like Amazon, Google, and Meta. Variants such as reversing nodes in k-groups or reversing subarrays test similar skills around pointer manipulation and boundary handling.

What data structure is used in Reverse K Subarrays?

The problem primarily uses arrays and the two-pointer technique. Two pointers move from the start and end of each k-sized segment to swap elements until the segment is reversed.

What is the time complexity of Reverse K Subarrays?

The optimal solution runs in O(n) time because every element is visited a constant number of times during the segment reversals. Space complexity is O(1) when reversing segments directly inside the array.

3865. Reverse K Subarrays - Practice Online

You are given an integer array nums of length n and an integer k.

You must partition the array into k contiguous subarrays of equal length and reverse each subarray.

It is guaranteed that n is divisible by k.

Return the resulting array after performing the above operation.

Example 1:

Input: nums = [1,2,4,3,5,6], k = 3

Output: [2,1,3,4,6,5]

Explanation:

The array is partitioned into k = 3 subarrays: [1, 2], [4, 3], and [5, 6].
After reversing each subarray: [2, 1], [3, 4], and [6, 5].
Combining them gives the final array [2, 1, 3, 4, 6, 5].

Example 2:

Input: nums = [5,4,4,2], k = 1

Output: [2,4,4,5]

Explanation:

The array is partitioned into k = 1 subarray: [5, 4, 4, 2].
Reversing it produces [2, 4, 4, 5], which is the final array.

Constraints:

1 <= n == nums.length <= 1000
1 <= nums[i] <= 1000
1 <= k <= n
n is divisible by k.