求二叉树中节点的最大距离

#include<iostream>
using namespace std;

struct Node
{
 char data;
 int nMaxLeft;
 int nMaxRight;
 Node* left;
 Node* right;
};

int nMaxLen;

int FindMaxLen(Node* pRoot)  //求二叉树中节点的最大距离
{
 if(pRoot==NULL)return NULL;
 if(pRoot->left==NULL)pRoot->nMaxLeft=0;
 if(pRoot->right==NULL)pRoot->nMaxRight=0;
 if(pRoot->left!=NULL)
 {
  FindMaxLen(pRoot->left);
 }
 if(pRoot->right!=NULL)
 {
  FindMaxLen(pRoot->right);
 }
 //计算左子树最长节点距离
 if(pRoot->left!=NULL)
 {
     int nTempMax=0;
  if(pRoot->left->nMaxLeft>pRoot->left->nMaxRight)
  {
   nTempMax=pRoot->left->nMaxLeft;
  }
  else
  {
   nTempMax=pRoot->left->nMaxRight;
  }
  pRoot->nMaxLeft=nTempMax+1;
 }
 //计算右子树最长节点距离
 if(pRoot->right!=NULL)
 {
     int nTempMax=1;
  if(pRoot->right->nMaxLeft>pRoot->right->nMaxRight)
  {
   nTempMax=pRoot->right->nMaxLeft;
  }
  else
  {
   nTempMax=pRoot->right->nMaxRight;
  }
  pRoot->nMaxRight=nTempMax+1;
 }
 //更新最长距离
 if(pRoot->nMaxLeft+pRoot->nMaxRight > nMaxLen)
 {
  nMaxLen=pRoot->nMaxLeft+pRoot->nMaxRight;
 }
}
Node* createTree()  //先根建树
{
     char ch;
  Node* p;
  cin>>ch;
  if(ch=='#')return NULL;
     p=new Node();
  p->data=ch;
  p->left=createTree();
  p->right=createTree();
  return p;
}
int main()
{
     while(true)
  {
   nMaxLen=0;
      Node* pRoot=createTree(); //先根建树
   FindMaxLen(pRoot);        //求二叉树中节点的最大距离
   cout<<"nMaxLen= "<<nMaxLen<<endl;
  }
  system("pause");
  return 0;
}