Thread: Sorting an Array of Structures

Hi All,

I think I have a simple problem here that's befuddling me: an ADT unsorted list that needs to be sorted by item number. I'm having a problem passing that array to a function defined in a class called "List".

Here's what I have set up so far:

Code:

struct DataRecord
{
	int        DataNumber;
	string   DataName;
};

const int MAX_ITEMS = 50;		
DataRecord DataItem[MAX_ITEMS];		
int count;			
typedef int ItemType;

// defining class

class List
{

public:
	
	List();
	void SortData();

private:

	int length;
	ItemType DataItem[MAX_ITEMS];
	
};

// *********** MAIN ******************

int main()
{
	ReadData( DataItem, count, MAX_ITEMS );
	//this works.  I can get the data into the array.

	void List::SortData ();          //this doesn't work

       return 0;
}

// ********** List::SortData Function **************

 void List::SortData()
 {
        ItemType temp;
        int passCount = 0;
        int minIndex;
        int searchIndex;

    for (passCount = 0; passCount < count - 1; passCount++)
    {
      minIndex = passCount;
               
      for (searchIndex = passCount + 1; 
            searchIndex < count; searchIndex++) 
       {

         // evaluate DataNumber

         if (DataItem[searchIndex].DataNumber < DataItem[minIndex].DataNumber)

         minIndex = searchIndex;

         // swap DataItem[minIndex] with DataItem[passCount]

         temp = DataItem[minIndex];
         DataItem[searchIndex] = DataItem[passCount];
         DataItem[passCount] = temp;			

        } // ends INNER for loop
		
     } // ends OUTER for loop

  return;
 }

For some reason the Sort function does not recognize the structure variables, specifically, DataNumber.

Any help or direction would be appreciated,
bob2509

I tried that and this is what I got:

C:\c++\Project2_beta2\Project2_beta2\Project2_beta 2.cpp(703) : error C2228: left of '.DataNumber' must have class/struct/union type

It's still not recognizing the structure values.

You have two variables called DataItem

One of them is global (the one you read data into) with
> ReadData( DataItem, count, MAX_ITEMS );

The other one is a private member within your List class

Guess which one your list member function will try and access
beep - correct, the one in the class.

They're also of different types - DataRecord and ItemType, which doesn't help matters

A quick fix is to say which DataItem you want
Eg.

Code:

if ( :: DataItem[searchIndex].DataNumber < :: DataItem[minIndex].DataNumber)

The :: is the scope operator, which should reference the global var (and not the class member).

You might want to rethink what is going on here...

I put the class in a header file and still get the same error.

Here's the header file:

Code:

const int MAX_ITEMS = 100;		// Variable Decleration
typedef int ItemType;

// defining class

class List
{

public:
	
	List();
	void SortInfo();
	void Print();

private:

	int length;
	ItemType ItemDB[MAX_ITEMS];
	
};

And here's the function I get the error in:

Code:

 void List::SortInfo()
 {
	 ItemType temp;
	 int passCount = 0;
	 int minIndex;
	 int searchIndex;

    for (passCount = 0; passCount < count - 1; passCount++)
	{
		minIndex = passCount;

		for (searchIndex = passCount + 1; searchIndex < count; searchIndex++) 
		{
			if (ItemDB[searchIndex].ItemNumber < ItemDB[minIndex].ItemNumber)
				minIndex = searchIndex;

			// swap ItemDB[minIndex].ItemNumber with ItemDB[passCount].ItemNumber

			temp = ItemDB[minIndex];
			ItemDB[searchIndex] = ItemDB[passCount];
			ItemDB[passCount] = temp;			

		} // ends INNER for loop
		
	} // ends OUTER for loop

	return;
 }

Here's the error being generated:

C:\c++\Project2_beta2\Project2_beta2\Project2_beta 2.cpp(684) : error C2228: left of '.ItemNumber' must have class/struct/union type

Please Help.

> typedef int ItemType
...
> ItemType ItemDB[MAX_ITEMS];

Which is just a long way of saying

int ItemDB[MAX_ITEMS];

It has no .members, because it isn't a structure

Sorry if I'm a bit confusing here. I'm trying to take an unsorted list and sort it by itemNumber. The ReadInfo function takes in the data as unsorted. The SortInfo function then is suppose to sort it. I am not allowed to use pointers or qsort.