3254. Find the Power of K-Size Subarrays I
Difficulty: Medium
Topics: Array, Sliding Window
You are given an array of integers nums of length n and a positive integer k.
The power of an array is defined as:
- Its maximum element if all of its elements are consecutive and sorted in ascending order.
- -1 otherwise.
You need to find the power of all subarrays1 of nums of size k.
Return an integer array results of size n - k 1, where results[i] is the power of nums[i..(i k - 1)].
Example 1:
- Input: nums = [1,2,3,4,3,2,5], k = 3
- Output: [3,4,-1,-1,-1]
-
Explanation: There are 5 subarrays of nums of size 3:
- [1, 2, 3] with the maximum element 3.
- [2, 3, 4] with the maximum element 4.
- [3, 4, 3] whose elements are not consecutive.
- [4, 3, 2] whose elements are not sorted.
- [3, 2, 5] whose elements are not consecutive.
Example 2:
- Input: nums = [2,2,2,2,2], k = 4
- Output: [-1,-1]
Example 3:
- Input: nums = [3,2,3,2,3,2], k = 2
- Output: [-1,3,-1,3,-1]
Constraints:
- 1
- 1 5
- 1
Hint:
- Can we use a brute force solution with nested loops and HashSet?
Solution:
We can break down the task as follows:
Problem Breakdown:
- We are given an array nums of length n, and a positive integer k. We need to consider all subarrays of size k and compute their power.
- The power of a subarray is:
- The maximum element of the subarray if all the elements are consecutive and sorted in ascending order.
- -1 otherwise.
- We need to return an array of size n - k 1, where each element corresponds to the power of the respective subarray.
Plan:
- Sliding Window Approach: We will slide over the array and check each subarray of length k.
- Check if the Subarray is Sorted: We need to check if the subarray has elements that are consecutive and sorted in ascending order.
- Return Maximum or -1: If the subarray is valid, we return the maximum element. Otherwise, return -1.
Steps:
-
Check if the subarray is sorted:
- A sorted subarray with consecutive elements should have the property: nums[i 1] - nums[i] == 1 for every i in the subarray.
-
Sliding Window:
- For each subarray of length k, check if it is sorted and return the maximum element if valid, otherwise return -1.
Let's implement this solution in PHP: 3254. Find the Power of K-Size Subarrays I
<?php /** * @param Integer[] $nums * @param Integer $k * @return Integer[] */ function resultsArray($nums, $k) { ... ... ... /** * go to ./solution.php */ } // Test cases print_r(resultsArray([1, 2, 3, 4, 3, 2, 5], 3)); // Output: [3, 4, -1, -1, -1] print_r(resultsArray([2, 2, 2, 2, 2], 4)); // Output: [-1, -1] print_r(resultsArray([3, 2, 3, 2, 3, 2], 2)); // Output: [-1, 3, -1, 3, -1] ?>
Explanation:
- Sliding Window: We use a for loop from i = 0 to i = n - k to consider all subarrays of size k. For each subarray, we use array_slice() to extract the subarray.
- Sorting Check: For each subarray, we check if it is sorted with consecutive elements by iterating through the subarray and checking if each pair of consecutive elements has a difference of 1.
- Result: If the subarray is valid, we append the maximum value of the subarray to the result. Otherwise, we append -1.
Time Complexity:
- We are iterating over n - k 1 subarrays.
- For each subarray, we check if the elements are consecutive, which takes O(k) time.
- Thus, the overall time complexity is O((n - k 1) * k) which simplifies to O(n * k).
Edge Case Considerations:
- If k = 1, every subarray is trivially sorted (it only contains one element), and the power of each subarray will be the element itself.
- If the subarray is not consecutive, it will immediately return -1.
Example Outputs:
- For nums = [1, 2, 3, 4, 3, 2, 5], k = 3, the output is [3, 4, -1, -1, -1].
- For nums = [2, 2, 2, 2, 2], k = 4, the output is [-1, -1].
- For nums = [3, 2, 3, 2, 3, 2], k = 2, the output is [-1, 3, -1, 3, -1].
This solution should efficiently work for the problem constraints.
Contact Links
If you found this series helpful, please consider giving the repository a star on GitHub or sharing the post on your favorite social networks ?. Your support would mean a lot to me!
If you want more helpful content like this, feel free to follow me:
- GitHub
-
Subarray: A subarray is a contiguous non-empty sequence of elements within an array. ↩
The above is the detailed content of Find the Power of K-Size Subarrays I. For more information, please follow other related articles on the PHP Chinese website!

In PHP, you can use session_status() or session_id() to check whether the session has started. 1) Use the session_status() function. If PHP_SESSION_ACTIVE is returned, the session has been started. 2) Use the session_id() function, if a non-empty string is returned, the session has been started. Both methods can effectively check the session state, and choosing which method to use depends on the PHP version and personal preferences.

Sessionsarevitalinwebapplications,especiallyfore-commerceplatforms.Theymaintainuserdataacrossrequests,crucialforshoppingcarts,authentication,andpersonalization.InFlask,sessionscanbeimplementedusingsimplecodetomanageuserloginsanddatapersistence.

Managing concurrent session access in PHP can be done by the following methods: 1. Use the database to store session data, 2. Use Redis or Memcached, 3. Implement a session locking strategy. These methods help ensure data consistency and improve concurrency performance.

PHPsessionshaveseverallimitations:1)Storageconstraintscanleadtoperformanceissues;2)Securityvulnerabilitieslikesessionfixationattacksexist;3)Scalabilityischallengingduetoserver-specificstorage;4)Sessionexpirationmanagementcanbeproblematic;5)Datapersis

Load balancing affects session management, but can be resolved with session replication, session stickiness, and centralized session storage. 1. Session Replication Copy session data between servers. 2. Session stickiness directs user requests to the same server. 3. Centralized session storage uses independent servers such as Redis to store session data to ensure data sharing.

Sessionlockingisatechniqueusedtoensureauser'ssessionremainsexclusivetooneuseratatime.Itiscrucialforpreventingdatacorruptionandsecuritybreachesinmulti-userapplications.Sessionlockingisimplementedusingserver-sidelockingmechanisms,suchasReentrantLockinJ

Alternatives to PHP sessions include Cookies, Token-based Authentication, Database-based Sessions, and Redis/Memcached. 1.Cookies manage sessions by storing data on the client, which is simple but low in security. 2.Token-based Authentication uses tokens to verify users, which is highly secure but requires additional logic. 3.Database-basedSessions stores data in the database, which has good scalability but may affect performance. 4. Redis/Memcached uses distributed cache to improve performance and scalability, but requires additional matching

Sessionhijacking refers to an attacker impersonating a user by obtaining the user's sessionID. Prevention methods include: 1) encrypting communication using HTTPS; 2) verifying the source of the sessionID; 3) using a secure sessionID generation algorithm; 4) regularly updating the sessionID.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

Dreamweaver CS6
Visual web development tools

SAP NetWeaver Server Adapter for Eclipse
Integrate Eclipse with SAP NetWeaver application server.

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

Atom editor mac version download
The most popular open source editor

Safe Exam Browser
Safe Exam Browser is a secure browser environment for taking online exams securely. This software turns any computer into a secure workstation. It controls access to any utility and prevents students from using unauthorized resources.
