Сортировка данных

#include <iostream>
 
using namespace std;
 
char shift(char *in)
{
 char item, *out = in;
 item = in[0]; *in++;
 while (*out++ = *in++);
 return item;
};
 
size_t push(char *in, char item)
{
 in[strlen(in)+1] = '\0';
 in[strlen(in)] = item;
 return strlen(in);
};
 
char *merge(char *left, char *right)
{
 size_t i = strlen(left)+strlen(right)+1;
 char *result = new char[i];
 result[0] = '\0';
 
 while (strlen(left) && strlen(right))
 {
  if (left[0] <= right[0])
  push(result, shift(left));
  else
  push(result, shift(right));
 }
 
 while (strlen(left))
 push(result, shift(left));
 
 while (strlen(right))
 push(result, shift(right));
 
 return result;
};
 
char *slice(char *in, size_t begin, size_t end)
{
 char *out = new char[strlen(in)];
 size_t i = 0, b = begin;
 while (b != end)
 {
  out[i] = in[b];
  i++; b++;
 }
 out[i] = '\0';
 return out;
};
 
char *merge_sort(char *in)
{
 size_t middle1;
 switch(strlen(in))
 {
  case 0:
  case 1:
  return in;
  default:
  middle1 = (strlen(in) * 1) / 2;
  return merge(merge_sort(slice(in, 0, middle1)),merge_sort(slice(in, middle1, strlen(in))));
 }
};
 
int main()
{
char a[11] = "7182930465", b[27] = "qazxswedcvfrtgbnhyujmkiolp", c[37] = "z0pa9q1ol2kwisx8c7duej3m4nrhfyv6b5gt";
cout << "sample a: " << a << endl;
cout << "sorted a: " << merge_sort(a) << endl << endl;
cout << "sample b: " << b << endl;
cout << "sorted b: " << merge_sort(b) << endl << endl;
cout << "sample c: " << c << endl;
cout << "sorted c: " << merge_sort(c);
system("pause > 0");
return 0;
}