Hackerrank - Circular Array Rotation

Hackerrank – Problem Statement

A description of the problem can be found on Hackerrank.

Solution

We rotate the array in circles. That why it is enough to calculate a position after all rotations using modulo. We split the array into two halves at position array_length - calculated_position. We change halves and concat them – the second will be first and the first will be the second.

I created solution in:

Scala
Java
JavaScript
Ruby

All solutions are also available on my GitHub.

Java

import java.util.*;

public class CircularArrayRotation {

    public static void main(String[] args) {
        Scanner stdin = new Scanner(System.in);
        int n = stdin.nextInt();
        int k = stdin.nextInt();
        int q = stdin.nextInt();
        List<Integer> numbers = new ArrayList<>(n);
        for(int i = 0; i < n; i++) {
            numbers.add(stdin.nextInt());
        }
        int[] queries = new int[q];
        for(int i = 0; i < q; i++) {
            queries[i] = stdin.nextInt();
        }
        int rotationPos = k % n;
        List<Integer> part1 = numbers.subList(0, numbers.size() - rotationPos);
        List<Integer> part2 = numbers.subList(numbers.size() - rotationPos, numbers.size());
        List<Integer> finalList = new ArrayList<>(part2);
        finalList.addAll(part1);

        for(int i = 0; i < q; i++) {
            System.out.println(finalList.get(queries[i]));
        }
        stdin.close();
    }
}

import java.util.*;

public class CircularArrayRotation {

public static void main(String[] args) {

Scanner stdin = new Scanner(System.in);

int n = stdin.nextInt();

int k = stdin.nextInt();

int q = stdin.nextInt();

List<Integer> numbers = new ArrayList<>(n);

for(int i = 0; i < n; i++) {

numbers.add(stdin.nextInt());

}

int[] queries = new int[q];

for(int i = 0; i < q; i++) {

queries[i] = stdin.nextInt();

}

int rotationPos = k % n;

List<Integer> part1 = numbers.subList(0, numbers.size() - rotationPos);

List<Integer> part2 = numbers.subList(numbers.size() - rotationPos, numbers.size());

List<Integer> finalList = new ArrayList<>(part2);

finalList.addAll(part1);

for(int i = 0; i < q; i++) {

System.out.println(finalList.get(queries[i]));

}

stdin.close();

}

JavaScript

'use strict';

const processData = input => {
    const lines = input.split('\n');
    const [n, k, q] = lines[0].split(' ').map(i => parseInt(i));
    const elements = lines[1].split(' ').map(i => parseInt(i));
    const queries = lines.slice(2).map(i => parseInt(i));
    const rotationPos = k % n;
    const part1 = elements.slice(0, n - rotationPos);
    const part2 = elements.slice(n - rotationPos);
    const finalArray = part2.concat(part1);
    for(let i = 0; i < q; i++) {
        console.log(finalArray[queries[i]]);
    }
};

process.stdin.resume();
process.stdin.setEncoding("ascii");

let _input = "";
process.stdin.on("data", input => _input += input);
process.stdin.on("end", () => processData(_input));

'use strict';

const processData = input => {

const lines = input.split('\n');

const [n, k, q] = lines[0].split(' ').map(i => parseInt(i));

const elements = lines[1].split(' ').map(i => parseInt(i));

const queries = lines.slice(2).map(i => parseInt(i));

const rotationPos = k % n;

const part1 = elements.slice(0, n - rotationPos);

const part2 = elements.slice(n - rotationPos);

const finalArray = part2.concat(part1);

for(let i = 0; i < q; i++) {

console.log(finalArray[queries[i]]);

}

};

process.stdin.resume();

process.stdin.setEncoding("ascii");

let _input = "";

process.stdin.on("data", input => _input += input);

process.stdin.on("end", () => processData(_input));

Scala

import scala.io.Source

object CircularArrayRotation extends App {
  val lines = Source.stdin.getLines().toList
  val line1 = lines.head.split(" ").map(_.toInt)
  val (n, k, q): (Int, Int, Int) = line1 match {
    case (List(a, b, c)) => (a, b, c)
    case Nil => throw new IllegalArgumentException
  }
  val elements = lines.tail.head.split(" ").map(_.toInt)
  val ms = lines.tail.tail.map(_.toInt)
  val rotationPos = k % n
  val parts = elements.splitAt(elements.length - rotationPos)
  val newElements = parts._2.toList ::: parts._1.toList
  ms.foreach(m => {
    println(newElements(m))
  })
}

import scala.io.Source

object CircularArrayRotation extends App {

val lines = Source.stdin.getLines().toList

val line1 = lines.head.split(" ").map(_.toInt)

val (n, k, q): (Int, Int, Int) = line1 match {

case (List(a, b, c)) => (a, b, c)

case Nil => throw new IllegalArgumentException

}

val elements = lines.tail.head.split(" ").map(_.toInt)

val ms = lines.tail.tail.map(_.toInt)

val rotationPos = k % n

val parts = elements.splitAt(elements.length - rotationPos)

val newElements = parts._2.toList ::: parts._1.toList

ms.foreach(m => {

println(newElements(m))

})

}

Ruby

(n, k, q) = gets.split(" ").map(&:to_i)
elements = gets.split(" ").map(&:to_i)
queries = []
q.times do
  queries << gets.to_i
end

rotationPos = k % n
part1 = elements.slice(0, n - rotationPos)
part2 = elements.slice(n - rotationPos, n)
final_array = part2.concat(part1)

q.times do |i|
  puts final_array[queries[i]]
end

(n, k, q) = gets.split(" ").map(&:to_i)

elements = gets.split(" ").map(&:to_i)

queries = []

q.times do

queries << gets.to_i

end

rotationPos = k % n

part1 = elements.slice(0, n - rotationPos)

part2 = elements.slice(n - rotationPos, n)

final_array = part2.concat(part1)

q.times do |i|

puts final_array[queries[i]]

end

Pavol Pidanič

I can count to 1023 with 10 fingers

Hackerrank – Circular Array Rotation