排序算法：堆排序

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shanql 2022-12-07 15:06:19 博主文章分类：算法 ©著作权

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#include <iostream>

using namespace std;


//自上而下调整成小顶堆
//nArray[iFrom+1,.....,iTo]是一个小顶堆
void AdjustHeapFromTopToDown( int nArray[], int iFrom, int iTo )
{
  if ( iFrom < 0 || iTo < 0 || iFrom >= iTo )
  {
    return;
  }

  //数组索引从0开始，左孩子2(i+1)-1,右孩子2(i+1)
  int nTemp = nArray[iFrom];
  int i = 2*(iFrom+1) - 1;
  while( i <= iTo )//存在左孩子
  {
    if ( ( (i+1) <= iTo ) && nArray[i+1] < nArray[i] )
    {
      i = i + 1;//右孩子更小
    }

    if ( nArray[i] < nTemp )
    {
      nArray[(i-1)/2] = nArray[i];

      i = 2*(i+1) - 1;
    }
    else
    {
      break;
    }
  }

  nArray[(i-1)/2] = nTemp;

}

void HeapSort( int nArray[], int nCount )
{
  if ( nCount <= 0 )
  {
    return;
  }

  //将数组调整成一个小顶堆
  for( int i = ( nCount - 2 ) / 2; i >= 0; --i )
  {
    AdjustHeapFromTopToDown( nArray, i, nCount - 1 );
  }

  //排序
  for ( int i = 0; i < nCount; ++i )
  {
    cout << nArray[0] << " ";

    //将堆中最后一个元素赋给堆的根结点，重新自上而下调整
    nArray[0] = nArray[nCount-1-i];
    AdjustHeapFromTopToDown( nArray, 0, nCount-1-i );
  }
  cout << endl;
}


int main()
{
  int nArray[] = { 6, 7, 3, 5, 4, 9, 0, 0, 11, 23, 3, 2, 1, 12, 13, 14, 15, 16, 17, 1, 2, 3, 
    4, 4, 5, 6, 7, 9, 8, 7, 6, 5, 4, 89, 78, 90 };
  HeapSort( nArray, _countof(nArray) );


  return 0;
}