关于二叉树，建立、遍历、求节点最大距离

今天做了一题求二叉树节点的最大距离，顺便写了下二叉树的建立，遍历的过程。

我觉得这题的主要思想是深度遍历+动态规划，我们在深度遍历的过程中，对于某一个子树，求出左右子树叶子节点到根节点的最大距离，进而求出经过根节点的最大距离。 最后求出所有子树经过根节点的最大距离。就是这个题目的最终结果。代码如下：

//二叉树的建立，以及遍历
//16 14 8 2 -1 -1 4 -1 -1 7 1 -1 -1 -1 10 9 -1 -1 3 -1 -1
//16 14 8 2 -1 -1 4 -1 -1 7 1 -1 -1 -1 -1
void  BuildBTree(BTreeNode* &pRoot)
{
	int nTemp;
	cin >> nTemp;
	if (nTemp == -1)
	{
		pRoot = NULL;
	}
	else
	{
		pRoot = new BTreeNode();
		pRoot->nValue = nTemp;

		BuildBTree(pRoot->pLeft);
		BuildBTree(pRoot->pRight);
	}
}

void PreOrderBTree(BTreeNode* pRoot)
{
	if (pRoot == NULL)
	{
		return;
	}

	cout << pRoot->nValue << " ";
	PreOrderBTree(pRoot->pLeft);
	PreOrderBTree(pRoot->pRight);
}

void MidOrderBTree(BTreeNode* pRoot)
{
	if (pRoot == NULL)
	{
		return;
	}
	MidOrderBTree(pRoot->pLeft);
	cout << pRoot->nValue << " ";
	MidOrderBTree(pRoot->pRight);
}

void PostOrderBTree(BTreeNode* pRoot)
{
	if (pRoot == NULL)
	{
		return;
	}
	PostOrderBTree(pRoot->pLeft);
	PostOrderBTree(pRoot->pRight);
	cout << pRoot->nValue << " ";
}

int  GetMaxNodeMaxDistance(BTreeNode* pRoot)
{
	if (pRoot == NULL)
	{
		return -1;
	}

	//左子树叶子结点到根结点的最大距离
	int max_left_distance = GetMaxNodeMaxDistance(pRoot->pLeft);
	//右子树叶子结点到根结点的最大距离
	int max_right_distance = GetMaxNodeMaxDistance(pRoot->pRight);
	//每个子树节点的最大距离
	int max_root_distance = max_left_distance + max_right_distance + 2;
	//比较每个子树节点的最大距离
	if (max_root_distance > max_distance)
	{
		max_distance = max_root_distance;
	}

	return max_left_distance > max_right_distance ? max_left_distance+1 : max_right_distance+1;
}

int max_distance = 0;
int main()
{

	BTreeNode* Root = NULL;
	BuildBTree(Root);

	cout << "----------------Build End------------------" << endl;
	system("pause");
	cout << "PreOrderBTree:" << endl;
	PreOrderBTree(Root);
	cout << endl << "MidOrderBTree:" << endl;
	MidOrderBTree(Root);
	cout << endl << "PostOrderBTree:" << endl;
	PostOrderBTree(Root);
	cout << endl << "GetMaxNodeMaxDistance:" << endl;
	GetMaxNodeMaxDistance(Root);
	cout << max_distance << endl;

	system("pause");
   return 0;
}

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