Juggling algorithm regarding Right Array rotation - c++

Question

Recently I learnt about the array rotation in linear time using Juggling algorithm. Here is the snippet regarding the left rotation of the array.
void ArrayRotate (int A[], int n, int k)
{
int d=-1,i,temp,j;
for(i=0;i<gcd(n,k);i++)
{
j=i;
temp=A[i];
while(1)
{
d=(j+k)%n;
if(d==i)
break;
A[j]=A[d];
j=d;
}
A[j]=temp;
}
}
but now I am stuck as how to use this Juggling algorithm to rotate the array in the Right Direction.
1,2,3,4,5 (given array)
5,1,2,3,4 (after 1 right rotation)
(I had solved this question using the brute force method and reversal method.)

Answer 1

As already mentioned, you should use std::rotate if you are allowed to.
Your implementation has a bug. Here is a fixed implementation.
void ArrayRotate(int A[], int n, int k) {
int d = -1, i, temp, j;
int g = gcd(n, k);
for (i = 0; i < g; ++i) {
j = i;
temp = A[i];
while (true) {
d = (j + k) % n;
if (d == i) {
break;
}
A[j] = A[d];
j = d;
}
A[j] = temp;
}
}
Also note that I took out gcd calculation out of loop condition. It does not technically affect complexity, but it's enough to compute the gcd only once.
To rotate the array k times to the right, just rotate it n - k times to the left.
void ArrayRotateRight(int A[], int n, int k) {
ArrayRotate(A, n, n - k);
}
Or change the 8th line to be d = (j - k + n) % n;

Answer 2

Not sure if you're doing this as an intellectual exercise, or for production code, but for production code use the STL rotate algorithm:
#include<iostream>
#include<algorithm>
using namespace std;
void display(int* a, int length)
{
for (int i = 0; i < length; ++i)
cout << a[i] << " ";
cout << endl;
}
int main()
{
const int len = 5;
int arr[] = { 1,2,3,4,5 };
display(arr, len);
rotate(arr, arr + 1, arr + len); // arr + x means left by x
display(arr, len);
rotate(arr, arr + len - 1, arr + len); // arr + len - x means right by x
display(arr, len);
}