算法之快速排序

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define MAXLENGTH 21

typedef struct
{
    int key;
} Record;

typedef struct
{
    Record r[MAXLENGTH];
    int length;
} DataList;

void printList(DataList *list)
{
    int i = 0;
    for(i-0; i<list->length; i++)
    {
        printf("%d  ",list->r[i]);
    }
    printf("\n");
}

int partition(DataList *list,int i ,int j)
{
    int low = i;
    int high = j;
    int x = list->r[low].key;

    while(low<high)
    {
        while(list->r[high].key>=x&&low<high)
            high--;

        if(low<high)
        {
            list->r[low] = list->r[high];
            low++;
        }

        while(list->r[low].key<=x&&low<high)
            low++;

        if(low<high)
        {
            list->r[high]=list->r[low];
            high--;
        }

    }
    list->r[low].key = x;
    printf("low = %d\n",low);
    return low;
}

void quicksort(DataList *list,int i,int j)
{
    int mod;
    if(i<j)
    {
        mod = partition(list,i,j); //划分为左右两个子表
        quicksort(list,i,mod-1);   //对左子表快速排序
        quicksort(list,mod+1,j);    //对右子表快速排序
    }
}


int main()
{
    DataList *list = (DataList *)malloc(1*sizeof(DataList));
    memset(list,0,sizeof(DataList));

    srand(time(0));

    int m = 0;
    int index = 1;
    for(m=0; m<20; m++)
    {
        int i = 0;
        i = rand() % 100;
        list->r[index].key = i;
        list->length++;
        index++;
    }

    printList(list);

    int low = 1;
    int high =20;
    quicksort(list,low,high);

    printList(list);
}