Rotate Array in place

/***

Rotate a one-dimensional array of n elements to the right by k steps.

For instance, with n=7 and k=3,

the array {a, b, c, d, e, f, g} is rotated to {e, f, g, a, b, c, d}.

***/

//best performance: time: O(n) and memory: O(1)

//reverse

#include<iostream>

using namespace std;

void swap(char *c1, char *c2) {

       char t = *c1;

       *c1 = *c2;

       *c2 = t;

}

void reverse(char *a, int st, int ed) {

       if(st >= ed) return;

       swap(a+st, a+ed);

       reverse(a, st+1, ed-1);

}

void rotate(char *a, int sz, int k) {

       if (k>sz) return;

       reverse(a, 0, sz-1);

       reverse(a, 0, k-1);

       reverse(a, k, sz-1);

}

void main() {

       char a[] = {'a', 'b', 'c', 'd', 'e', 'f', 'g'};

       rotate(a, 7, 1);

       for (int i = 0; i<7; i++)

              cout<<a[i]<<", ";

       cout<<endl;

}