HOWTO: Quick Sorting Using MFC Carray-Derived Classes ID: Q216858
The Information in this Article Applies TO:
Microsoft Visual C , 32-Bit Editions, Versions 5.0, 6.0
Summary
This Article Shows You How To Quick-Sort AN MFC Carray-Derived Class. The Code Below Depends Only On The MFC and Visual C Run-Time Library.
More information
The Visual C Run-Time Library (MSVCRT) Implements The Quick-Sort Function, Qsort, As Follows:
Void Qsort (void * base, size_t num, size_t width, int (__cdecl * company) (const void * elem2);
The following example shows you how to use this function to sort an MFC CArray class. Although the following example uses a CString array, you can easily customize for other MFC CArray-derived classes, such as CByteArray, CDWordArray, CObArray, CPtrArray, CUintArray, And cwordArray.
Steps to Implement Sorting
Derive Your Array Data Class from One of the Carray-Derived Classes. IN Our EXAMPLE, WE Use CstringArray As The Base Class for Our Class. The Following Is The Declaration In The Heooter File:
Class CsortableStringArray: Public CSTRINGARRY: PUBLIC
{
PUBLIC:
protected:
}; To the public section of your class add the folload function:
Void Sort (StringComparefn PfnCompare = Compare); To the protected section of your class address:
static int __cdecl Compare (const CString * pstr1, const CString * pstr2);. Now add the following two type defs above the declaration of your class These typedefs later help us in passing pointers of the two functions that we declared in steps 2 and 3 To The Visual C Run-Time's Qsort Function:
Typedef int (__cdecl * genericcomparefn) (Const Void * ELEM2);
TYPEDEF INT (Const CString * Elem1, Const Cstring * Elem2); in Your .cpp file, IMPLEMENT THE TWO FUNCTIONS That You Declared Earlier: //
// sortableStringArray.cpp
//
INT CsortablestringArray :: Compare (const cstring * pstr2)
{
Assert (PSTR1);
AskERT (PSTR2);
Return PSTR1-> Compare (* PSTR2);
}
Void CsortableStringArray :: Sort (Stringcomparefn Pfncompare / * = CsortedStringArray :: Compare * /)
{
CString * prgstr = getdata ();
Qsort (prgstr, getsize (), sizeof (cstring), (genericcomparefn) pfncompare;
}
That Is It. Now Let's Look At the Contents of The Entire File:
//
// sortableStringArray.h
//
Typedef int (__cdecl * genericcomparefn) (Const Void * ELEM2);
TYPEDEF INT (CONST CSTRING * ELEM1, Const Cstring * ELEM2);
Class CsortableStringArray: Public CSTRINGARRY: PUBLIC
{
PUBLIC:
Void Sort (StringComparefn PFNCompare = Compare);
protected:
Static int __cdecl company (const cstring * pstr1, const cstring * pstr2);
}
//
// sortableStringArray.cpp
//
#include "sortableStringArray.h"
INT CsortablestringArray :: Compare (const cstring * pstr2)
{
Assert (PSTR1);
AskERT (PSTR2);
Return PSTR1-> Compare (* PSTR2);
}
Void CsortableStringArray :: Sort (Stringcomparefn Pfncompare / * = CsortedStringArray :: Compare * /)
{
CString * prgstr = getdata ();
Qsort (prgstr, getsize (), sizeof (cstring), (genericcomparefn) pfncompare;
}
To use the array in your code, Just Declare it and call the Sort () function. The folload example Uses this Array:
SRAND TIME (NULL); // generate seed for rand ().
CsortableStringArray Arr;
CString Str;
For (int i = 0; i <1000; i )
{
Str.Format ("% 6d", Rand ()); // Get a random number string.
Arr.Add (STR);
Trace ("% S / N", (LPCTSTSTSTST) STR);
}
Long ltim = gettickcount ();
Arr.sort ();
For (i = 0; i <1000; i )
{
Trace ("% S / N", (LPCTSTST) Arr [I]);
}
TRACE ("Time TOOK =% li / n", GetTickCount () - LTIM);
NOTE: To implement a CArray type other than CString, just derive your class from the other array types and modify the Sort () and the Compare () functions accordingly.NOTE: Quick Sort is a more efficient mechanism of sorting than the bubble sort used In The Microsoft Knowledge Base Article, "How to Sort A CstringArray In MFC" (Q120961)
References
For Additional Information About The Bubble Sort Method, Please See The Following Article In The Microsoft Knowledge Base:
Q120961 HOW SORT A CSTRINGARRAY IN MFC
Additional Query Words:
KeyWords: KBDatabase KBMFC KBODBC KBVC500 KBVC600 Version: Winnt: 5.0, 6.0 Platform: Winnt Issue Type: Kbhowto
Last Reviewed: February 4, 2000 © 2000 Microsoft Corporation. All Rights Reserved. Terms of Use.
