Codility - Cyclic Rotation (JavaScript) - Method 1 - Using JS Functions

Lesson 2 - Arrays

Many interviewers do not like this solution, although correct because it utilizes JavaScript functions. Method 2 will outline what tech recruiters often look for.

Task Description:
An array A consisting of N integers is given. Rotation of the array means that each element is shifted right by one index, and the last element of the array is moved to the first place. For example, the rotation of array A = [3, 8, 9, 7, 6] is [6, 3, 8, 9, 7] (elements are shifted right by one index and 6 is moved to the first place).

The goal is to rotate array A K times; that is, each element of A will be shifted to the right K times.

Write a function:
function solution(A, K);
that, given an array A consisting of N integers and an integer K, returns the array A rotated K times.

For example, given

A = [3, 8, 9, 7, 6]
K = 3
the function should return [9, 7, 6, 3, 8]. Three rotations were made:

[3, 8, 9, 7, 6] to [6, 3, 8, 9, 7]
[6, 3, 8, 9, 7] to [7, 6, 3, 8, 9]
[7, 6, 3, 8, 9] to [9, 7, 6, 3, 8]
For another example, given
A = [0, 0, 0]
K = 1
the function should return [0, 0, 0]

Given
A = [1, 2, 3, 4]
K = 4
the function should return [1, 2, 3, 4]

Assume that:
N and K are integers within the range [0..100];
each element of array A is an integer within the range [−1,000..1,000].
In your solution, focus on correctness. The performance of your solution will not be the focus of the assessment.

[-momorsy]

function rotation(A, R) {
for (let i = 0; i < R; i++) {
A.unshift(A[A.length - 1]);
A.pop();
}

return A;
}

[gidmanone]

I'm lost here. why is it necessary to reverse the Array after every pop( ) ?

[SaravanaKumar-kgzm]

This also gives the correct output

var a = [3, 8, 9, 7, 6]
for(i=0; i<3; i++) {
var pop = a.pop();
a.unshift(pop)
}

console.log(a)

[김정섭-yn]

Below is output without using built-on library

function solution(A, K) {
// Handle edge cases
if (A.length === 0 || K === 0) {
return A;
}

// Calculate effective number of rotations
const effectiveRotations = K % A.length;

// Create a new array to store rotated elements
const rotatedArray = [];

// Iterate through the original array
for (let i = 0; i < A.length; i++) {
// Calculate the new index after rotation
const newIndex = (i + effectiveRotations) % A.length;
// Populate the rotated array
rotatedArray[newIndex] = A[i];
}

return rotatedArray;
}

// Test the function
console.log(solution([3, 8, 9, 7, 6], 2));