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



[cpp] view plaincopy

#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====\n");

for(id = 0 ; id< 10;id++)

{

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

}printf("=====before====\n");

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===\n\n");

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===\n\n");

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===\n\n");

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;

}