学步园

#include "iostream"
#include "vector"
#include "algorithm"
using namespace std;
void HeapAdjust(std::vector<int> &a,int i,int size){
	int lchild = 2*i + 1;
	int rchild = 2*i + 2;
	int max = i;
	if(i < size/2 ){
		if(lchild<size&&a[lchild]>a[max]) max = lchild;
		if(lchild<size&&a[rchild]>a[max]) max = rchild;
		if(max != i){
			swap(a[i],a[max]);
			HeapAdjust(a,max,size);
		}
	}
}
void BuildHeap(std::vector<int> &a,int k){
	for (int i = k-1; i >= 0; --i)
	{
		HeapAdjust(a,i,k);
	}
}
int main(int argc, char const *argv[])
{
	std::vector<int> a(6);
	a[0] = 3;a[1] = 11; a[2] = 8;a[3] = 2;
	a[4] = 9;a[5] = 4;
	int k = 3;//取前k最小的
	BuildHeap(a,k);
	for (int i = k; i < a.size(); ++i)
	{
		if(a[0] > a[i]) {
			swap(a[0],a[i]);
			HeapAdjust(a,0,k);
		}
	}
	for (int i = 0; i < k; ++i)
	{
		cout<<a[i]<<"\t";
	}
	return 0;
}