算法导论 习题6.2-5 用迭代法实现堆排序

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#include <iostream>
using namespace std;

void swap(int array[] , int i , int j)
{
    array[i] = array[i]+array[j];
    array[j] = array[i]-array[j];
    array[i] = array[i]-array[j];
}
void MaxHeapify(int array[] , int i , int hSize)
{
    int l = 2*i;
    int r = 2*i+1;
    int largest;
    while(l <= hSize)
    {
        if(array[l] > array[i])
        {
            largest = l;
        }
        else
        {
            largest = i;
        }
        if(r<=hSize && array[r]>array[largest])       //It's r<=hSize other than r<hSize.
        {
            largest = r;
        }
        if(largest != i)
        {
            swap(array , i ,largest);
            i = largest;
            l = 2*i;
            r = 2*i+1;
        }
        else
        {
            break;
        }
    }
}

void BuildMaxHeap(int array[] , int hSize)
{
    for(int i=hSize/2 ; i>=1 ; i--)
    {
        MaxHeapify(array , i , hSize);
    }
}

void HeapSort(int array[] , int length)
{
    int hSize = length;
    BuildMaxHeap(array , hSize);
    for(int i=length ; i>=2 ; i--)
    {
        swap(array , 1 , i);
        hSize--;
        MaxHeapify(array , 1 , hSize);
    }
}
int main()
{
    int a[99];
    for(int i=1 ; i<99 ; i++)
    {
        a[i] = rand()%100;
    }
    HeapSort(a,99);
    for(int i=1 ; i<99 ; i++)
    {
        cout << a[i] << ' ';
    }
    return 0;
}

 


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