写一个quick sort

#include <stdio.h>

#include <stdlib.h>

//int a[]={1000,10000,9,10,30,20,50,23,90,100,10};

int a[]={10,9,8,7,6,5};

int length=sizeof(a)/sizeof(int);

int swap(int start, int stop){

	int temp;

	temp=a[start];

	a[start]=a[stop];

	a[stop]=temp;

	return 0;

}

int  quicksort(int start, int stop) {

	int i;

	int ostart=start;

	int ostop=stop;

	int k=a[start];

	int middle;

	if(start >= stop){

		return 0;

	}

	while( start <= stop ){

		printf("\n begin start=%d,stop=%d ,k=%d , ostart=%d,ostop=%d\n" , start, stop, k,ostart,ostop);

		int i;

		for(i=0;i<length;i++){

			printf("%d\n" , a[i]);

		}

		while((a[stop] >= k) &&(start<stop)){

			stop--;

		}

		while( (a[start] < k)  &&(start<stop)){

			start++;

		}

		if(start >= stop){

			break;

		}

		printf("after move start=%d,stop=%d ,k=%d , ostart=%d,ostop=%d\n" , start, stop, k,ostart,ostop);

	    if( start < stop ){

			swap(start,stop);

		}

		printf("may after swap start=%d,stop=%d ,k=%d , ostart=%d,ostop=%d\n" , start, stop, k,ostart,ostop);

	}

	quicksort(ostart, start);

	quicksort(stop+1, ostop);

}

int main(){

	printf("length= %d\n",length);

	int i;

	printf("\n");

	quicksort(0,length-1);

	printf("\n\n\n");

	for(i=0;i<length;i++){

		printf("%d\n" , a[i]);

	}

	printf("\n");

	return 0;

}

　　虽然这种算法烂大街，但是实现一个简洁、正确的算法还是不容易的。