Codility before lunch

  • Posted on: 30 August 2017
  • By: Jackson

Like how new recruits in the army are required to do a few pull-ups before lunch, I make myself complete at least 2 Codility challenges a week. If nothing, it helps to keep the mind thinking algorithmically - which I believe is a good thing.

This challenge requires one to cycle through a series of numbers in an array for N times. For example, given the array A = [3,8,9,7,6], to cycle this function once, it becomes A = [6,3,8,9,7]. Notice that the last element becomes the first, and then every other element moves 1 place up. 

To cycle it twice, it becomes A = [7,6,3,8,9].

To cycle it thrice, it becomes A = [9,7,6,3,8]. 

In essence, you are removing the last element, and then moving every element up by 1 place, and then putting the last element back into the first place. 

To achieve this, I used 2 loops, one to iterate through every element in the array and moving them up, and another one to do it n times.

Made a mistake in my first attempt because I did not consider the case of an empty array. Total time taken to code: 10 minutes. I have earned my lunch today.

function solution(A, K) {
   var holder;
   if (A.length != 0){
     for (var j = 1; j <= K; j++){
        for (var i=A.length-1; i>= 0; i--){
          if (i == A.length-1){
            holder = A[i];
          A[i] = A[i-1];
        A[0] = holder;
   return A;



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