求一颗二叉树中最远的两个节点的距离

#include <iostream>
using namespace std;
typedef struct tagNode
{
	char data;
	tagNode *lchild;
	tagNode *rchild;
}*PNode;
void createtree(PNode &T)
{
	char c;
	cin >> c;
	if(c == ',')return;
	else
	{
		T = new tagNode;
		T->data = c;
		T->lchild = NULL;
		T->rchild = NULL;
		createtree(T->lchild);
		createtree(T->rchild);
	}
}

int helper(const PNode T, const PNode root)
{
	if( T == NULL)return 0;

	int ldepth = helper(T->lchild,root);
	int rdepth = helper(T->rchild,root);
	if( T == root)
		return ldepth+rdepth+1;
	else
	 	return max(ldepth,rdepth)+1;
}
int TreeMaxDistance(PNode T)
{
	helper(T,T);
}

int main()
{
	PNode T = NULL;
	createtree(T);
	if( T == NULL)return 0;
	cout << TreeMaxDistance(T) << endl;;
}