堆排序

注意理解用数组表示堆以及运用好递归。

 

#include <stdlib.h>

int a[] = {0,2,6,8,4,10};

void swap(int* a, int i, int j)
{
	int temp = a[i];
	a[i] = a[j];
	a[j] = temp;
}

void HeapAdjust(int* a, int i, int size)
{
	int lchild = 2 * i;
	int rchild = 2 * i + 1;
	int max = i;
	if(i <= size / 2)
	{
		if(lchild <= size && a[lchild] > a[max])
		{
			max = lchild;
		}
		if(rchild <= size && a[rchild] > a[max])
		{
			max = rchild;
		}
		
		if(max != i)
		{
			swap(a, i, max);
			HeapAdjust(a, max, size);
		}
	
	}
}

void BuildHeap(int* a, int size)
{
	int i;
	for(i = size/2; i >= 1; i--)
	{
		HeapAdjust(a, i, size);	
	}
}

void HeapSort(int* a, int size)
{
	BuildHeap(a, size);
	int i;	
	for(i = size; i >= 1; i--)
	{
		swap(a, 1, i);
		HeapAdjust(a, 1, i - 1);
	}
}

void print(int *a, int size)
{
	int i;
	for(i = 1; i <= size; i++)
	{
		printf(" %d ",a[i]);
	}
}

int main()
{
	HeapSort(a, 5);
	print(a, 5);
}