快速排序的三种写法的效率比较

 

分类： C++ C语言 数据结构 2012-09-02 20:26 459人阅读 评论(0) 收藏 举报

数据结构算法null

            最近在复习排序和查找算法的时候，回想算法课程和数据结构课程上面各种写法，总结一下，顺便比较了一下它们之间的效率，

另《外数据结构》书本上阐述，如果比较的枢纽值不是第一个或者最后一个而是 a[low] ,a[high],a[(high+low)/2] 的中间值，效率还会好很多，但是我在实现的过程中，总是搬移到了错误的位置，没有实现

#include <iostream.h>
#include <windows.h>
#include <ctime>
#include <math.h>
#include <cstdlib>
#include <stdio.h>

void QuickSort( int a[],int low,int high);  //比较经典的一种，将往中间扫面时找到的满足条件的交换
void QuickSort3( int a[],int low,int high); //枢纽暂存，每次找到一个比枢纽大或者小的，就放到上一次搬离的位置，最后把枢纽放回到low处（低地址必须小于高地址，不能等于）
 void QuickSort2( int a[],int low,int high);    //只有一个while，指针都从头部开始，，快指针每次都向后移动，遇到一个比枢纽大的就和慢指针交换值

//产生随机数
int randArr(int * pint , int size);

int size = 0;
int main()
{
     int a[] ={4,-2,3,19,0,-4,99,7,2,-5,0,-11,2,2,56,-8,0,17,200,5,1,3,5,4,6,-5,29,-1,8};
     int b[] ={ 34,51,38,65,119,76,16,27};
      //int b[] ={76, 119 };
    int tsize=150000;
     int *pint = new int[tsize];
     int *pint2 = new int[tsize];
     int *pint3 = new int[tsize];
     int id = 5;

     if(! randArr(pint,tsize) )
        return 0;
//   memcpy(pint ,a,sizeof(int) * tsize);
     memcpy(pint2,pint,sizeof(int) * tsize);
     memcpy(pint3,pint,sizeof(int) * tsize);

     size = tsize;
    printf("=====before====
");
     for(id = 0 ; id< 10;id++)
     {
            printf("%3d ", pint[id]);
     }printf("=====before====
");

    int start  = GetTickCount();

     QuickSort(pint,0,size -1);
    cout<<"time QuickSort used="<< GetTickCount() - start << endl;
     for(id = 0 ; id< 10;id++)
     {
            printf("%3d ", pint[id]);
     }printf("======QuickSort===

");


     start  = GetTickCount();

     QuickSort2(pint2,0,size -1);
    cout<<"time QuickSort2 used="<< GetTickCount() - start << endl;
     for(id = 0 ; id< 10;id++)
     {

        printf("%3d ", pint2[id]);

     }printf("======QuickSort2===

");

     QuickSort3(pint3,0,size -1);
    cout<<"time QuickSort3 used="<< GetTickCount() - start << endl;
     for(id = 0 ; id< tsize;id++)
     {
         if(pint[id] != pint2[id])
         {
            printf("Confliction!! %d",id);
            break;
         }


     }printf("======QuickSort3===

");

     return 0;
}

void QuickSort(int a[],int l,int h)
{
    int po;
    int high = h , low = l;
    if(low < high )
    {
        po = a[l];
        low++;
        while(1)
        {
            while(low <=  high && a[high] >= po) high--;
            while(low <=  high && a[low] <= po) low++;

            if(low < high)
            {
                a[low] ^= a[high];
                a[high] ^= a[low];
                a[low] ^= a[high];
                low++;
                high--;
            }
            else
                break;
        }
         a[l] =   a[high];
        a[high]  = po;

        QuickSort(a,l,high-1);
        QuickSort(a,high+1,h);
    }


}

void QuickSort2(int a[],int l ,int h)
{
    int po;
    int high = h,low = l;
    if( l < h )
    {
        po = a[l];
        while( low < high)
        {
            while( low < high && a[high] >= po ) high--;
            a[low] = a[high];
            while( low < high && a[low] <= po ) low++;
            a[high] = a[low];
        }
        a[low] = po;

        QuickSort2(a,l,low-1);
        QuickSort2(a,low+1,h);
    }
}


void QuickSort3(int a[],int l ,int h )
{
    int high  = l+1, low = l+1;
    int po = a[l];

    if( l < h)
    {
        while( high <= h)
        {
            if( a[high] < po)    //找到慢指针
            {
                if(high != low)
                {
                    a[low] ^=a[high];
                    a[high] ^=a[low];
                    a[low] ^=a[high];
                }
                low++;
            }
            high++;
        }

        if(low-1 != l)
        {
            a[low-1] ^=a[l];
            a[l] ^=a[low-1];
            a[low-1] ^=a[l];
        }

        low--;
        QuickSort3(a,l,low - 1);
        QuickSort3(a,low+1 ,h);


    }
}



int randArr(int * pint , int size)
{
    int i = 0;
    if(!pint)   return 0;
    srand((unsigned int)time(NULL));

    for( i = 0 ; i<size; i++)
    {
            pint[i] = rand() % 100 ;
            if( rand() % 10 == 1 && rand() % 10 == 1 && rand() % 10 == 1 &&pint[i] % 10 == 2)
                pint[i] *= -1;
    }
    return 1;
}