制作一个递归的函数进行绘制:
void drawSubTree( BiTreeNode* pNode, QPainter* pPainter, int gap )
{
drawCircle( pPainter, gap );
if ( pNode->lchild != Q_NULLPTR )
{
drawSubTree( pNode->lchild, gap / 2 );
}
if ( pNode->rchild != Q_NULLPTR )
{
drawSubTree( pNode->rchild, gap / 2 );
}
}