快速排序-堆排序-STL中的堆排序-归并排序 》时间比较

// 转自：by MoreWindows( http://blog.csdn.net/MoreWindows )

//就时间而言，快速排序还是比较快的，其次是归并排序。STL中的堆排序与堆排序几乎时间相等
#include <cstdio>
#include <algorithm>
#include <ctime>
using namespace std;
//------------------------快速排序----------------------------
void quick_sort(int s[], int l, int r)
{
if (l < r)
{
int i = l, j = r, x = s[l];
while (i < j)
{
while(i < j && s[j] >= x) // 从右向左找第一个小于x的数
j--;
if(i < j)
s[i++] = s[j];

while(i < j && s[i] < x) // 从左向右找第一个大于等于x的数
i++;
if(i < j)
s[j--] = s[i];
}
s[i] = x;
quick_sort(s, l, i - 1); // 递归调用
quick_sort(s, i + 1, r);
}
}
//------------------------归并排序----------------------------
//将有二个有序数列a[first...mid]和a[mid...last]合并。
void mergearray(int a[], int first, int mid, int last, int temp[])
{
int i = first, j = mid + 1;
int m = mid,   n = last;
int k = 0;

while (i <= m && j <= n)
{
if (a[i] < a[j])
temp[k++] = a[i++];
else
temp[k++] = a[j++];
}

while (i <= m)
temp[k++] = a[i++];

while (j <= n)
temp[k++] = a[j++];

for (i = 0; i < k; i++)
a[first + i] = temp[i];
}
void mergesort(int a[], int first, int last, int temp[])
{
if (first < last)
{
int mid = (first + last) / 2;
mergesort(a, first, mid, temp);    //左边有序
mergesort(a, mid + 1, last, temp); //右边有序
mergearray(a, first, mid, last, temp); //再将二个有序数列合并
}
}
bool MergeSort(int a[], int n)
{
int *p = new int
;
if (p == NULL)
return false;
mergesort(a, 0, n - 1, p);
return true;
}
//------------------------堆排序---------------------------
inline void Swap(int &a, int &b)
{
int c = a;
a = b;
b = c;
}
//建立最小堆
//  从i节点开始调整,n为节点总数 从0开始计算 i节点的子节点为 2*i+1, 2*i+2
void MinHeapFixdown(int a[], int i, int n)
{
int j, temp;

temp = a[i];
j = 2 * i + 1;
while (j < n)
{
if (j + 1 < n && a[j + 1] < a[j]) //在左右孩子中找最小的
j++;

if (a[j] >= temp)
break;

a[i] = a[j];     //把较小的子结点往上移动,替换它的父结点
i = j;
j = 2 * i + 1;
}
a[i] = temp;
}
//建立最小堆
void MakeMinHeap(int a[], int n)
{
for (int i = n / 2 - 1; i >= 0; i--)
MinHeapFixdown(a, i, n);
}
void MinheapsortTodescendarray(int a[], int n)
{
for (int i = n - 1; i >= 1; i--)
{
Swap(a[i], a[0]);
MinHeapFixdown(a, 0, i);
}
}
const int MAXN = 5000000;
int a[MAXN];
int b[MAXN], c[MAXN], d[MAXN];
int main()
{
int i;
srand(time(NULL));
for (i = 0; i < MAXN; ++i)
a[i] = rand() * rand(); //注rand()产生的数在0到0x7FFF之间

for (i = 0; i < MAXN; ++i)
d[i] = c[i] = b[i] = a[i];

clock_t ibegin, iend;

printf("--当前数据量为%d--By MoreWindows(http://blog.csdn.net/MoreWindows)--\n", MAXN);
//快速排序
printf("快速排序:  ");
ibegin = clock();
quick_sort(a, 0, MAXN - 1);
iend = clock();
printf("%d毫秒\n", iend - ibegin);

//归并排序
printf("归并排序:  ");
ibegin = clock();
MergeSort(b, MAXN);
iend = clock();
printf("%d毫秒\n", iend - ibegin);

//堆排序
printf("堆排序:  ");
ibegin = clock();
MakeMinHeap(c, MAXN);
MinheapsortTodescendarray(c, MAXN);
iend = clock();
printf("%d毫秒\n", iend - ibegin);

//STL中的堆排序
printf("STL中的堆排序: ");
ibegin = clock();
make_heap(d, d + MAXN);
sort_heap(d, d + MAXN);
iend = clock();
printf("%d毫秒\n", iend - ibegin);
return 0;
}