二叉堆

Posted 2020-09-19 菜菜

根据算法导论里的伪代码实现

#include <iostream>
using namespace std;

void exchange(int a[], int i, int j)
{
	int temp = a[i];
	a[i] = a[j];
	a[j] = temp;
}
void adjustTree(int a[], int i, int total)
{
	int l = i * 2;
	int r = i * 2 + 1;
	//取左右孩子中最大的
	int maxIndex = -1;
	if(l <= total && a[l] > a[i])
	{
		maxIndex = l;
	}
	else
		maxIndex = i;
	if(r <= total && a[r] > a[maxIndex])
	{
		maxIndex = r;
	}
	if(maxIndex != i)
	{
		exchange(a, i, maxIndex);
		//TODO 优化
		adjustTree(a, maxIndex, total);
	}
}

void buildTree(int a[], int total)
{
	for(int i = total / 2; i >= 1; i--)
	{
		adjustTree(a, i, total);
	}
}

/**
 * 大堆
 */
int main()
{
	int a[] = { 0, 4, 1, 3, 2, 16, 9, 10, 14, 8, 7 };
	int total = 10;
	buildTree(a, total);
	for(int i = 1; i <= total; i++)
		cout << " " << a[i];
	cout << endl;
	int t2 = total;
	for(int i = total; i >= 2; i--)
	{
		exchange(a, 1, t2);
		t2--;
		adjustTree(a, 1, t2);
	}
	for(int i = 1; i <= total; i++)
		cout << " " << a[i];
	cout << endl;
	return 0;
}