Dynamic Array Question

[satchmo05]

Hi, my question to you all is how do I store values into a dynamic array?! If I have this chunk of code:

while (break_apart >> word)
  {
    front = &word.at(0);
    rear = &word.at(word.size() - 1);
    while (front <= rear)
    {
          swap (*front, *rear);
          front++;
          rear--;
    }
    cout << word << " ";
  }

(If you were wondering about what this code is supposed to do --> it should input "Hello" and output "olleH", and this chunk is the meat of the program)

So, how would I store each newly modified word into a dynamic array? If you need more of my code, just let me know and I can post it up. Thank you to all who help in advance!!

[guestgulkan]

Any reason why you can't use a vector (of strings) ?

[satchmo05]

how would it look if it were a vector of strings?

[satchmo05]

ok, so if it were a vector of strings, I would want to .push_back each word to store it at the end of the vector correct? essentially copying the components. so, I think I did that correctly, the code is posted below, but how would I display that vector of strings. the way I have obviously doesn't work. please let me know. Thank you for all of the help!!

#include <iostream>
#include <sstream>
#include <string>
#include <vector>  
void swap (char *front, char *rear); 
using namespace std;
 
int main()
{
  string input, word;
  char *front, *rear; 
  vector <string> array; 

  cout << "Enter a sentence that you would like to reverse: ";
  getline(cin, input);
 
  istringstream break_apart(input);
  
  while (break_apart >> word)
  {
    front = &word.at(0);
    rear = &word.at(word.size() - 1);
    while (front <= rear)
    {
          swap (*front, *rear);
          front++;
          rear--;
    }
    array.push_back(word);
    cout << array << " ";
  }

  return 0;
}
void swap (char *front, char *rear)
{
     char temp = *front;
     *front = *rear;
     *rear = temp;
}

Thanks again!

[guestgulkan]

Here is one way:

#include <iostream>
#include <sstream>
#include <string>
#include <vector>  

void swap (char *front, char *rear);
 
using namespace std;int main()
{
  string input, word;
  char *front, *rear; 
  vector <string> array; 

  cout << "Enter a sentence that you would like to reverse: ";
  getline(cin, input);
 
  istringstream break_apart(input);
  
  while (break_apart >> word)
  {
    front = &word.at(0);
    rear = &word.at(word.size() - 1);
    while (front <= rear)
    {
          swap (*front, *rear);
          front++;
          rear--;
    }
    array.push_back(word);
   
  }
  
  //print out the vector
  vector<string>::iterator itr; //declare an iterator of the right type
  //loop through array vector using iterator
  for (itr = array.begin(); itr != array.end(); ++itr)
  {
    cout << *itr << " ";
  }
    
    
  return 0;
}
void swap (char *front, char *rear)
{
     char temp = *front;
     *front = *rear;
     *rear = temp;
}

[satchmo05]

i get an error message:

`array' cannot be used as a function

Also, because .begin and .end were supposedly not declared, i changed those, and this is the error message i get...thanks though for the help! I was messing around with the code, going with what I know (i'm not too familiar with vectors), so I tried out some with a dynamic array of type char and this is what i got, but i don't know what to put in the for loop...

typedef char* ArrayPtr;
  ArrayPtr array;
  array = new char[1000];
  istringstream break_apart(input); // Puts the sentence into a stream
  
  while (break_apart >> word)
  {
    front = &word.at(0); //Assigns leading pointer variable to the first character of the word
    rear = &word.at(word.size() - 1); //Assigns ending pointer variable to the last character of the word
    while (front <= rear) //Allows both even AND odd length words to be used without complications
    {
          swap (*front, *rear);
          front++;
          rear--;
    }
    cout << word << " ";
  }

  for (int i = 0; i < input.length(); i++)
  {
      //WHAT DO I PUT HERE?!?
  }

Thanks again for your help!

[guestgulkan]

Did you copy my code correctly - it certainly works.

[satchmo05]

oh yeah, you're right, sorry. can you explain what you coded from line 33 to 39 please? thanks

[guestgulkan]

will do later - must go and do the day job now - and it looks as if it going to be an annoying pain in the a*se day.

[satchmo05]

haha, ok, thanks!

[guestgulkan]

Are you acquainted with the c++ Standard template Library?

[satchmo05]

no i am not, do tell ;)

[eker676]

In order to be a better program you have to be somewhat self reliant.
Usually when I see something that I don't know about, I use the handy search engine called google.

STL includes maps, vectors, lists, deques, etc. for storing and manipulating data. Look at the reference section on this site for more information.

[guestgulkan]

For an introduction to vectors, refer to the c++ reference on this very site (saves me typing)
http://www.cplusplus.com/reference/stl/vector/


An iterator is a STL object that behaves like a pointer.
Consider the following standard C/C++ code:

   #define ARRAY_MAX 5
   int  int_array[ARRAY_MAX] = {1,2,3,4,5}; //an array
   int *int_ptr; // a pointer to iterate through the array
  for (int_ptr = int_array;  int_ptr != int_array+ARRAY_MAX;  ++int_ptr)
  {
    
    cout << *int_ptr << endl;
  }
  

we have an array. We want to loop through the array, so we declare a pointer of the correct type int *int_ptr; and set it to the start of the array int_ptr = int_array;.
Each time round the loop we get the current value at the pointer and do something with it cout << *int_ptr << endl;.
We make sure that we don't step past the end of the array int_ptr < int_array+ARRAY_MAX; and we update the iterator each time round the loop ++int_ptr

The C++ STL designers have developed a direct replacement template class for the standard array called the vector.
The vector has what is called an interator - which is as we have said is a type of pointer.
The vector has a class method called begin() which returns an iterator or pointer
to the first elemen in the vector.
It also has a method called end() which returns a pointer to the element which is ONE past the last element in the vector.
To get the elecment currently being pointed at the iterator we use the familiar *pointer
notation, and to increment the iterator we use the familiar ++pointer notation.

So your code using vectors would be :

  //print out the vector
  vector<string>::iterator itr; //declare an iterator of the right type - in this case string
  //loop through array vector using iterator
  for (itr = array.begin(); itr != array.end(); ++itr)
  {
    cout << *itr << " ";
  }

The vector is a direct replacement for the standard array and much better and safer to use.
There are other 'containers' int the STL, like queues, stack, lists,........
Does that make sense?