快速SELECT算法

#include <iostream>
#include <algorithm>
using namespace std;

int a[] = {
		4, 3, 6, 8, 10, 9, 2, 5, 7, 1
	};

void select(int a[], int lhs, int rhs, int k)
{
	if(lhs > rhs || k < 0)
		return;
	int i = lhs, j = rhs, pivot = a[lhs];
	
	while(i < j)
	{
		while(a[j] >= pivot && i < j)
			j--;
		while(a[i] <= pivot && i < j)
			i++;
		if(i < j)
		{
			int t = a[i];
			a[i] = a[j];
			a[j] = t;
		}
	}
	if(i == j)
	{
		a[lhs] = a[i];
		a[i] = pivot;

		for(int l = 0; l < 10; ++l)
			cout << a[l] << " ";
		cout << endl;
		if(i-lhs> k)
			select(a, lhs, i - 1, k);
		else if(i-lhs < k)
			select(a, i + 1, rhs, k - i + lhs - 1);
		else
			return;
	}
	return;
}

int main(void)
{
	int k = 7;//7
	select(a, 0, 9, k);
	for(int i = 0; i < k; ++i)
		cout << a[i] << " ";
	cout << endl;
	
	return 0;
}