快速排序

程式碼：

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
int partition(int a[], int p, int r)
{
	int t, i, j;
	/*隨機化
	int x = p + (rand() % (r - p));
	t = a[r];
	a[r] = a[x];
	a[x] = t;
	*/
	i = p - 1;
	for (j = p; j < r; j++)
		if (a[j] <= a[r])
			{
				i++;
				t =
 
 a[i];
				a[i] = a[j];
				a[j] = t;
			}
	t = a[r];
	a[r] = a[i + 1];
	a[i + 1] = t;
	return i + 1;
}
void sort(int a[], int p, int r)
{
	/*普通遞迴，對於<8,7,6,5,4,3,2,1>棧深度為8
	if (p < r)
	{
		int q = partition(a, p, r);
		sort(a, p, q - 1);
		sort(a, q + 1, r);
	}
	*/

	/*尾遞迴，對相同陣列呼叫時，棧深度為5
	while(p < r)
	{
		int q = partition(a, p, r);
		sort(a, p, q - 1);
		p = q + 1;
	}
	*/
 


	/*尾遞迴，且每次遞迴呼叫劃分時較短的子陣列，對相同陣列呼叫時，棧深度為2（Θ（lgn））*/
	while (p < r)
	{
		int q = partition(a, p, r);
		if (q <= (p + r) / 2)
		{
			sort(a, p, q - 1);
			p = q + 1;
		}
		else
		{
			sort(a, q + 1, r);
			r = q - 1;
		}
	}
}
void main()
{
	int n, i, a[30000];
	scanf("%d", &n);
	for (i = 1; i <= n;
 
 i++)
		scanf("%d", a + i);
	sort(a, 1, n);
	for (i = 1; i <= n; i++)
	{
		if (i % 30 == 0)
			printf("\n");
		printf("%d ", a[i]);
	}
	getchar();
	getchar();
}