Thread: Need Help On an Assignment

I'm working on an assignment and am very new to a lot of the concepts it wants me to do.

I have not finished the code yet. As of now I simply want to see if my code looks correct and I have some questions about the assignment itself. Below is my assignment is below that is my current code.

I haven't yet gotten to member function 1, so you don't have to read there and beyond yet. All I've done is added the names to the header.

~~~

Instructions: In this lab you will create a class for a Dynamic Array of Strings. This class may be useful for future projects. The class will provide the following functionality:

Get a string from the array

Add a string to the front or back of the array

Delete a string from the front or back of the array

Get the number of strings in the array

Get the maximum capacity of the array

Clear the array

Sort the array

Get the array as a comma separated list

Ability to grow on demand

For Extra Credit you can add the following:

Save the array to a file

Retrieve a previous saved array from a file

Class –DynamicStringArray:
Contains a dynamic array of dynamic strings.

Private Data Members:
A dynamic array of dynamic strings, i.e. a dynamic array of string*s.
An integer to hold the maximum capacity of your array.
An integer to hold the current size of your array.

Default Constructor:
Initializes the array to 10 elements and initializes the elements to NULL.

Overloaded Constructor:
Initializes the array via an unsigned integer parameter. If the parameter's valueis not valid (i.e. 0) set the array to a capacity of 10. Initializes all elements to NULL.

Destructor:
Frees the memory for all strings
Frees the memory for the dynamic string* array

Member Function 1:
Named At. Has one parameter, anunsigned integer that corresponds to a location in the array. If that location doesn't exist in the array throw the string "Invalid Location". If the location does exist return a pointer to the string.

Member Function 2:
Named GetFirst. Returns a pointer to the first string in the array. If the array is empty throw the string "Array Empty".

Member Function 3:
Named GetLast. Returns a pointer to the first string in the array. If the array is empty throw
the string "Array Empty".

Member Function 4:
Named AddFront. Has one parameter, a dynamic string. Adds this string to the beginning of the array. Note: this requires you to shift all the elements in the array. If the array is full increase the capacity of the array (call the IncreaseCapacityfunction) and then add the dynamic string.

Member Function 5:
Named AddBack. Has one parameter, a dynamic string. Adds this string to the end of the array. If the array is full increase the capacity of the array (call the IncreaseCapacityfunction) and then add the dynamic string.

Member Function 6:
Named DeleteFront. Deletes the first element in the array. Note: this requires you to shift all the elements in the array. If the array is empty throw the string "Array Empty".

Member Function 7:
Named DeleteBack. Deletes the last element in the array. If the array is empty throw the string "Array Empty".

Member Function 8:
Named GetSize. Returns an unsigned integer that is the current size of the array. This is a const function.

Member Function 9:
Named GetCapacity. Returns an unsigned integer that is the current maximum capacity of the array. This is a const function.

Member Function 10:
Named Empty. Returns a Boolean. True if the array's size is 0. This is a const function.

Member Function 11:
Named Clear. Deletes all of the dynamic strings in the array and sets the size of the array to 0.

Member Function 12:
Named Sort. Sorts the array A-Z. You must use the private function ToUpper as this helps when comparing strings of mixed case.

Member Function 13:
Named ToString. Returns a string containing all of the strings in
the array, comma separated.

Overloaded Friend operator<<:

Outputs a comma separated list of all of the strings in the array.

Private Member Function 1:
Named IncreaseCapacity. Increases the capacity of the array by 10. Note: this requires you making a second dynamic array and "copying" over the original data.

Private Member Function 2:
Named ToUpper. Takes a string as a parameter and returns that
same string with all the characters uppercased.


~~~

Code:

#include "dynamic_string_array.h"
#include <iostream>
#include <cmath>
#include <string>
#include <cctype>
#include <sstream>
using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::stringstream;

DynamicStringArray::DynamicStringArray() {
  int *myarray[10] = {};
}

DynamicStringArray::DynamicStringArray(int arraymax = 10) {
  arraymax_ = arraymax;
  int *myarray[arraymax] = {};
}

DynamicStringArray::~DynamicStringArray() {
  delete[] arraysize_;
}

Code:

#ifndef DYNAMIC_STRING_ARRAY_H
#define DYNAMIC_STRING_ARRAY_H
#include <string>
#include <climits>

class DynamicStringArray {
private:
  int arraymax_;
  int arraysize_;
  IncreaseCapacity();
  ToUpper();
public:
  DynamicStringArray();
  At(unsigned int Loc);
  GetFirst();
  GetLast();
  AddFront(string *str);
  AddBack(string *str);
  DeleteFront();
  DeleteBack();
  GetSize();
  GetCapacity();
  Empty();
  Clear();
  Sort();
  ToString();
}

#endif /* DYNAMIC_STRING_ARRAY_H */

~~~
Questsions:

1) As of now does my code look correct? I want to make sure I at least have the basics done before moving on to the rest of it.

2) What does the assignment mean when it says "return a pointer"?

1. Some of this I can figure out (like 10 is bool), but I have no idea what the return type would be on something like the first function. Can you tell me?

2. So I'm guessing that needs to be changed?

Code:

int *myarray = new int[10];
int *myarray[10] = {};

Would this work for setting up the array and declaring everything NULL?

3. So would I need to do the above for that too?

I'm a tad confused. How does this set the arrays elements to NULL?

Code:

DynamicStringArray:ynamicStringArray()

{

     m_array = new char*[m_defaultIncrease];

     m_arraySize = m_defaultIncrease;

}

And is this code looking right now?

Code:

#include "dynamic_string_array.h"
#include <iostream>
#include <cmath>
#include <string>
#include <cctype>
#include <sstream>
using std::cin;
using std::cout;
using std::endl;
using std::string;
using std::stringstream;

DynamicStringArray::DynamicStringArray() {
  myarray = new char*[defaultincrease];
  arraysize = defaultincrease;
}

DynamicStringArray::DynamicStringArray(int arraymax = 10) {
  arraysize = arraymax;
  int *myarray[arraymax] = {};
}

DynamicStringArray::~DynamicStringArray() {
  delete[] arraysize_;
}

char * DynamicStringArray::At(const unsigned int i) {
  if((i < 0) || (i > myarray) {
    throw "Invalid Location";
  }
  return string* myarray->at(i);
}

Code:

#ifndef DYNAMIC_STRING_ARRAY_H
#define DYNAMIC_STRING_ARRAY_H
#include <string>
#include <climits>

class DynamicStringArray {
private:
  char** myarray;
  static const int defaultincrease = 10;
  int arraysize;
  int IncreaseCapacity();
  string ToUpper();
public:
  DynamicStringArray();
  char* At(unsigned int loc);
  char* GetFirst();
  char* GetLast();
  void AddFront(string *str);
  void AddBack(string *str);
  void DeleteFront();
  void DeleteBack();
  int* GetSize();
  int* GetCapacity();
  bool Empty();
  void Clear();
  string* Sort();
  string* ToString();
}

#endif /* DYNAMIC_STRING_ARRAY_H */

Well, I figured this part was setting up the array.

>>int *myarray[arraymax] = {};

I figured this part was setting up the maximum amount of elements it could have.

>>int *myarray[arraymax] = {};

And I figured this was setting it to NULL.

>>int *myarray[arraymax] = {};

I'm guessing I was way off then? ^^; I admit with the other part, I only had the vaguest idea of what I was doing.

I understand the concept, but I'm not sure what that has to do with what I'm currently doing.

Code:

DynamicStringArray::DynamicStringArray() {
  myarray = new char*[defaultincrease];
  arraysize = defaultincrease;
}

For example with this...this calls the array and sets it to 10 elements, but I'm not seeing how it would declare it all NULL. I've read before that this is how you set all the elements of an array to NULL

Code:

int *myarray[] = {};

But you said it was wrong and I'm not sure how else to do it.

Like this, right?

Code:

int array [3] = { 0, 4, 10 };

This?

Code:

int size;
int array [size] = {};