Skip to main content

Coding Exercise, Episode 1


I have received the following exercise from an interviewer, he didn't give the name of the problem. Honestly, I have no idea how to solve this problem even I have tried to read it three times before. Since I used to be a person who always tells myself "I am not the one good at algorithms", but giving up something too soon which I feel that I didn't spend enough effort to overcome is not my way. Then, I have sticked on it for 24 hours.

According to the given image on the problem, I tried to get more clues by searching. Thanks to Google, I found a similar problem on Hackerrank (attached link below). My target here was trying my best to just understand the problem and was trying to solve it accordingly by the Editorial on Hackerrank. Due to this circumstance, it turns me to love solving algorithms from now on (laugh). Check it out!

Problem

You are given a very organized square of size N (1-based index) and a list of S commands

The ith command will follow the format (a[i], b[i], d[i]) and will be executed as:

For every elements inside the inner-square whose top-left corner located at (a[i], b[i]) and bottom-right corner located at (a[i] + d[i], b[i] + d[i]) will rotate 90 degree clockwise. And the ith inner-square always contains (i + 1)th inner-square

E.g. If the input square with size N = 7 and command (2, 3, 3), the execution will be (image):

After executed S commands, you will then be asked to do L queries to determine the final location given the initial value w[i].
E.g. With the above example, the final position of 25 will be (4, 4) - its initial location was (4, 5)

Input format and constraints

- Line 1: integer N - size of the square (N <= 10^7)
- Line 2: integer S - number of commands (S <= 10^5)
- S subsequent lines: S commands with format (a[i], b[i], d[i]) with constraints
1 <= a[i], b[i] and 0 <= d[i] < N
a[i-1] <= a[i] and a[i] + d[i] <= a[i - 1] + d[i - 1]
b[i-1] <= b[i] and b[i] + b[i] <= b[i - 1] + b[i - 1]
The next line will contains integer L - number of queries (L <= 10^5)
Each subsequent line ask for the final position of a number w[i] (0 <= w[i] < N^2)

Here is one input example

7
2
1 2 4
2 3 3
2
11
24

Here is the output

4 4
2 5

Solution 

(with my commenting on the code)


Reference
[1]. https://www.hackerrank.com/challenges/king-richards-knights
Labels:

Comments

  1. UnknownJanuary 21, 2018 at 4:40 AM

    Holy shit, this is exactly the task that LenderRate has offered me back then xD.

    ReplyDelete

Post a Comment

Popular posts from this blog

DevOps for Dummies

Everyone talks about it, but not everyone knows what it is. Why DevOps? In general, whenever an organization adopts any new technology, methodology, or approach, that adoption has to be driven by a business need. Any kind of system that need rapid delivery of innovation requires DevOps (development and operations). Why? DevOps requires mechanisms to get fast feedback from all the stakeholders in the software application that's being delivered. DevOps approaches to reduce waste and rework and to shift resources to higher-value activities. DevOps aims to deliver value (of organization or project) faster and more efficiently. DevOps Capabilities The capabilities that make up DevOps are a broad set that span the software delivery life cycle. The following picture is a reference architecture which provides a template of a proven solution by using a set of preferred methods and capabilities. My Remarks Okay, that sounds cool. What does it simply mean, again? The f...
Post a Comment
Read more

AngularJS - Build a custom validation directive for using multiple emails in textarea

AngularJS already supports the built-in validation with text input with type email. Something simple likes the following: <input name="input" ng-model="email.text" required="" type="email" /> <span class="error" ng-show="myForm.input.$error.email"> Not valid email!</span> However, I used a text area and I wanted to enter some email addresses that's saparated by a comma (,). I had a short research and it looked like AngualarJS has not supported this functionality so far. Therefore, I needed to build a custom directive that I could add my own validation functions. My validation was done only on client side, so I used the $validators object. Note that, there is the $asyncValidators object which handles asynchronous validation, such as making an $http request to the backend. This is just my implementation on my project. In order to understand that, I supposed you already had experiences with ...
Post a Comment
Read more

Junit - Test fails on French or German string assertion

In my previous post about building a regex to check a text without special characters but allow German and French . I met a problem that the unit test works fine on my machine using Eclipse, but it was fail when running on Jenkins' build job. Here is my test: @Test public void shouldAllowFrenchAndGermanCharacters(){ String source = "ÄäÖöÜüß áÁàÀâÂéÉèÈêÊîÎçÇ"; assertFalse(SpecialCharactersUtils.isExistSpecialCharater(source)); } Production code: public static boolean isExistNotAllowedCharacters(String source){ Pattern regex = Pattern.compile("^[a-zA-Z_0-9_ÄäÖöÜüß áÁàÀâÂéÉèÈêÊîÎçÇ]*$"); Matcher matcher = regex.matcher(source); return !matcher.matches(); } The result likes the following: Failed tests: SpecialCharactersUtilsTest.shouldAllowFrenchAndGermanCharacters:32 null A guy from stackoverflow.com says: "This is probably due to the default encoding used for your Java source files. The ö in the string literal in the J...
5 comments
Read more

What the heck is Meteor DDP?

I was using Meteor for my messenger project. I was so curious about the real time connection. I wanted to know how exactly this mechanism works. In this post, I will go through the DDP Specification, an overview of WebSocket, and a simple demo about how to subscribe a publication of Rocket.Chat (containing a DDP server) from an external webpage. At a glance, I knew that Meteor invented a protocol called DDP which uses for handling real time connection. So then, what is DDP? "DDP (Distributed Data Protocol) is the stateful WebSocket protocol that Meteor uses to communicate between the client and the server." [1] All right! Why does DDP matter? "DDP is a standard way to solve the biggest problem facing client-side JavaScript developers: querying a server-side database, sending the results down to the client, and then pushing changes to the client whenever anything changes in the database" . [2] In order to understand deeply the protocol, I decided ...
Post a Comment
Read more

Strategy Design Pattern

For example, I have a program with an Animal abstract class and two sub-classes Dog and Bird. I want to add new behavior for the class Animal, this is "fly".  Now, I face two approaches to solve this issue: 1. Adding an abstract method "fly" into the class Animal. Then, I force the sub-classes should be implemented this method, something like: public abstract class Animal{ //bla bla public abstract void fly(); } public class Bird extends Animal{ //bla bla public void fly(){ System.out.println("Fly high"); } } public class Dog extends Animal{ //bla bla public void fly(){ System.out.println("Cant fly"); } } 2. Creating an interface with method "fly" inside. The same issue to an abstract class, I force the classes these implement this interface should have a method "fly" inside: public interface Flyable{ public void fly(); } public class Bird implements Flyable{ //bla bla public void fly(){ System.out.pr...
Post a Comment
Read more