[Chong]

Hi
It seems that your algorithm for quick sort is wrong. The following is the algorithm for quick sort. I hope this helps.
Best regards
Chong

+++++++++++++++++++++++++++++++++++++++++
// quicksort.cpp
//
//		This program shows how to use Quicksort to sort arrays.
//		Note that pivot in the program is nothing more than a guide!! It
//		is used just for a comparison!!
//

#include <stdio.h>
#include <string.h>
#include <conio.h> //for getche()
#include <windows.h>
#include <winbase.h>

#define		swap(x,y)	{ int t; t=x; x=y; y=t;}
#define		order(x,y)	if (x > y) swap(x,y)
#define		O2(x,y)		order(x,y)
#define		O3(x,y,z)	O2(x,y);O2(x,z);O2(y,z)

typedef enum {yes, no} yes_no;


static yes_no find_pivot(int *left, int *right, int *pivot_ptr);
static int *partition(int *left, int *right, int pivot);
void quicksort(int *left, int *right);


main( )
{
	int *p,pivot;
	int age[5] = {7,2,5,8,9};
	int len = sizeof(age)/sizeof(int);

	quicksort(age, age+len-1);

	for (int k=0; k<len; k++) {
		printf("[Age] %d\n", age[k]);
	} // for

	getche();

} // main


void quicksort(int *left, int *right)
{
	int *p;
	int pivot;

	if (find_pivot(left,right,&pivot) == yes) {
		p = partition(left,right,pivot);
		quicksort(left, p-1);
		quicksort(p, right);
	} // if

} // quicksort



static yes_no find_pivot(int *left, int *right, int *pivot_ptr)
{
	int a,b,c,*p;

	a = *left;
	b = *( left + (right-left)/2 );
	c = *right;

	O3(a,b,c);

	if (a < b) {
		*pivot_ptr = b;
		return (yes);
	} // if

	if (b < c) {
		*pivot_ptr = c;
		return(yes);
	} // if

	for ( p = left+1; p <= right; p++) {
		if (*p != *left) { 	
			*pivot_ptr = (*p < *left) ? *left: *p;
			return(yes);
		} // if
	} // for

	return(no);
} // find_pivot


static int *partition(int *left, int *right, int pivot)
{
	while (left <= right) {
		while (*left< pivot) ++left;
		while (*right >= pivot) --right;
		if (left < right) {
			swap(*left, *right);
			++left;
			--right;
		} // if
	} // while

	return(left);
} // partition