Algorithm to rotate an array in linear time

Question

How to rotate an integer array by i times using swap function only in linear time.

Answer 1

/* Q: How can we shift/rotate an array in place?
A: "in place" means O(1) space complexity, so we need to do some trick
 */

#include 
#include 
using namespace std;

void ArrayRotate(int a[], int n, int k)
{
    if (n < 1 || k % n == 0 ) return;

    k %= n;
    if (k < 0) k += n;

    reverse(a, a+k);
    reverse(a+k, a+n);
    reverse(a, a+n);
}

void PrintArray(int a[], int n)
{
    for ( int i = 0 ; i < n; ++i)
        cout << a[i] << " ";
    cout << endl;
}

int main()
{
    int a[] = { 1, 2 , 3, 4, 5 };
    int n = sizeof(a)/sizeof (a[0]);

    PrintArray(a, n);
    ArrayRotate(a, n, 2);
    PrintArray(a, n);

    return 0;
}
/* Output:
1 2 3 4 5
3 4 5 1 2
 */