12.19

（1） 快速排序算法的程序

 

 

#include<stdio.h>

#include<stdlib.h>

#include<time.h>

 

void printArray(int arr[], int size)

{

int i;

for (i = 0; i < size; i++)

printf("%d ", arr[i]);

printf("\n");

}

 

void swap(int *a, int *b)

{

int temp;

temp = *a;

*a = *b;

*b = temp;

}

 

void swap1(int arr[], int a, int b)

{

int temp = arr[a];

arr[a] = arr[b];

arr[b] = temp;

}

 

void median3(int A[], int left, int right)

{

int center = (left + right) / 2;

if (A[left] > A[center])

swap(&(A[left]), &(A[center]));

if (A[left] > A[right])

swap(&(A[left]), &(A[right]));

if (A[center] > A[right])

swap(&(A[center]), &(A[right]));

swap(&(A[center]), &(A[right - 1]));

}

 

 arr[] --> Array to be sorted,

  low  --> Starting index,

  high  --> Ending index */

void quickSort(int arr[], int low, int high)

{

if (low < high)

{

median3(arr, low, high);

int pivot = high - 1;

int i = low;

int j = high - 1;

while (1)

{

while (arr[++i] < arr[pivot]) {}

while (j > low && arr[--j] > arr[pivot]) {}

if (i < j)

{

swap1(arr, i, j);

}

else

{

break;

}

}

if (i < high)

{

swap1(arr, i, high - 1);

}

quickSort(arr, low, i - 1);

quickSort(arr, i + 1, high);

}

}

 

int arr[500000];

int main()

{

clock_t start, end;

srand(10086);

 

 

for (int j = 0; j < 500000; j++)

arr[j] = j;

int n = 500000;

 

 

start = clock();

quickSort(arr, 0, n - 1);

end = clock();

 

printf("time=%f\n", (double)(end - start) / CLOCKS_PER_SEC);

return 0;

}