reverse string with c++

#include <iostream>
#include <string>
using namespace std;
 
void recursiveReverse( char a[], int start, int end )
{
 int i, j;
 
 for(i=start; i<end; i++)
 {
 
  for(j=end;j>start;j--)
  {
   char temp = a[i];
   a[i]=a[j];
   a[j]=temp;
  }
 
 }
 
}
 
 
 
void stringReverse( char str[] )
{
  int length = strlen( str );
  recursiveReverse( str, 0, length - 1 );
}
 
int main()
{
 
  char a[20];
 
  for (int i = 0; i < 20; i++ )
  a[i] = 'A' + i;
  a[19] = '\0';
  cout << "string before reversing:  " << a << endl;
  stringReverse( a );
  cout << "string  after reversing:  " << a << endl;
  return 0;