非递归快速排序（待排记录数＜=3，使用直接插入排序）

/*
非递归快速排序
使用栈存放待排序列的首尾下标 
*/
#include <iostream>
#include <stack>
using namespace std;
int partition(int a[], int low, int high){
	int pivok = a[low];
	while(low<high){
		while(low<high && a[high]>pivok)	high--;
		a[low] = a[high];
		while(low<high && a[low]<pivok)		low++;
		a[high] = a[low];
	}
	a[low] = pivok;
	return low;
}
void insertSort(int a[], int low, int high){
	int i, j;
	int t;
	for(i=low+1; i<=high; i++){
		if(a[i] < a[i-1]){
			t = a[i];
			for(j=i-1; j>=low; j--){
				if(a[j] > t)	
					a[j+1] = a[j];
				else
					break;
			}
			a[j+1] = t;
		}
	}
}
void quickSort(int a[], int low, int high){
	if(high-low+1 <= 1)		//待排序列为空 或 只有一个元素
		return;
	
	if((high-low+1) <=3){	//待排序列个数少于3，使用比较排序
		insertSort(a, low, high);
		return;
	}
	
	//待排序列最少有3个，用快速排序 
	stack<int> s;	//用栈存储待排序列的首尾元素下标
	int mid = partition(a, low, high);
	if(mid > 1){	//有左子串
		s.push(low);
		s.push(mid-1);
	}
	if(mid < (high-low+1)-2){	//有右子串
		s.push(mid+1);
		s.push((high-low+1)-1);
	}
	
	while(!s.empty()){
		int right = s.top();
		s.pop();
		int left = s.top();
		s.pop();
		
		if((right-left+1) <3){	//待排序列个数少于3，使用比较排序
			insertSort(a, left, right);
		}else{		//待排序列最少为3
			mid = partition(a, left, right);
			if(left < mid-1){
				s.push(left);
				s.push(mid-1);
			}
			if(right > mid+1){
				s.push(mid+1);
				s.push(right);
			}
		}
	}
}
int main(){
	int a[] = {1,5,2,3,4};
	int len = sizeof(a)/sizeof(int);
	quickSort(a, 0, len-1);
	for(int i=0; i<len; i++)
		cout << a[i] << " ";
	cout << endl;
	return 0;
}