求二叉树节点的最大距离

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题目：求二叉树中节点的最大距离
距离就是节点到根节点的边数，最大距离必然是叶子节点间的距离

思路：
1.转化为子树上的解
2.递归遍历左右子树，计算左右子树的最长节点距离
3.更新最长节点距离

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struct Node
{
	int data;
	Node* pLchild;
	Node* pRchild;
	int nMaxLeft;//左子树最大距离
	int nMaxRight;//右子树最大距离
};

void FindMaxLen(Node* proot)
{
	//遍历到叶子节点返回
	if(proot == NULL)return;

	if(proot->pLchild == NULL)
		proot->nMaxLeft = 0;
	if(proot->pRchild ==NULL)
		proot->nMaxRight =0;

	if(proot->pLchild != NULL)//递归寻找左子树最大距离
		FindMaxLen(proot->pLchild);
	if(proot->pRchild != NULL)
		FindMaxLen(proot->pRchild);

	if(proot->pLchild != NULL)//计算左子树最长节点距离
	{
		int nMaxLen = 0;
		if(proot->pLchild->nMaxLeft > proot->pRchild->nMaxRight)
			nMaxLen = proot->pLchild->nMaxLeft;
		else
			nMaxLen = proot->pRchild->nMaxRight;

		proot->nMaxLeft = nMaxLen + 1;

	}
	if(proot->pRchild != NULL)//计算右子树最长节点距离
	{
		int nMaxLen = 0;
		if(proot->pRchild->nMaxLeft > proot->pRchild->nMaxRight)
			nMaxLen = proot->pLchild->nMaxLeft;
		else
			nMaxLen = proot->pRchild->nMaxRight;
		proot->nMaxLeft = nMaxLen + 1;
	}

	//更新最长距离
	if(proot->nMaxLeft +proot->nMaxRight > nMaxLen)
		nMaxLen = proot->nMaxLeft + proot->nMaxRight;

}