char str1[] = "abcdef", str2[] = "123456789";
  int len1, len2, i, j, k;

  while(str1[i]!='\0'){
    len1++; i++;
  }

  while(str2[j]!='\0'){
    len2++; j++;
  }

  i = j = 0;

  int resLen = len1+len2;
  char* result = new char[resLen];

  for(k = 0; k < resLen; i++, j++){

   if(i < len1) {
       result[k] = str1[i];
       k++;
   }

    if(j < len2) {
        result[k] = str2[j];
        k++;
    }
  }

  result[resLen+1] = '\0';

  cout << result;