题目:如果我们把二叉树看成一个图，父子节点之间的连线看成是双向的，我们姑且定义”距离”为两节点之间边的个数。写一个程序，求一棵二叉树中相距最远的两个节点之间的距离.
例如:
10
/ \
5 12
/ \
4 7
这棵树的话,最大距离为3.分别路径为4,5,10,12共3条边,7,5,10,12共3条边,所以最大距离为3.

递归的思想,分别考虑左右子树的,从根节点开始.

代码如下:

#include<iostream>
using namespace std;

struct BiTreeNode
{
    int m_nValue;
    BiTreeNode *m_pleft;
    BiTreeNode *m_pright;
    int m_nMaxLeft;
    int m_nMaxRight;
};

int nMaxLen = ;

void findMaxLen(BiTreeNode *pRoot);

void addBiTreeNode(BiTreeNode *&pCurrent, int value);


int main()
{
    BiTreeNode *pRoot = NULL;
    addBiTreeNode(pRoot, );
    addBiTreeNode(pRoot, );
    addBiTreeNode(pRoot, );
    addBiTreeNode(pRoot, );
    addBiTreeNode(pRoot, );

    findMaxLen(pRoot);
    cout<<nMaxLen<<endl;
    return ;
}



void findMaxLen(BiTreeNode *pRoot)
{
    if(pRoot == NULL)
        return ;

    if(pRoot->m_pleft == NULL)
        pRoot->m_nMaxLeft = ;

    if(pRoot->m_pright == NULL)
        pRoot->m_nMaxRight = ;

    if(pRoot->m_pleft != NULL)
        findMaxLen(pRoot->m_pleft);

    if(pRoot->m_pright != NULL)
        findMaxLen(pRoot->m_pright);

    if(pRoot->m_pleft != NULL)
    {
        int nTempMax = ;

        if(pRoot->m_pleft->m_nMaxLeft > pRoot->m_pleft->m_nMaxRight)
            nTempMax = pRoot->m_pleft->m_nMaxLeft;
        else
            nTempMax = pRoot->m_pleft->m_nMaxRight;

        pRoot->m_nMaxLeft = nTempMax + ;
    }

    if(pRoot->m_pright != NULL)
    {
        int nTempMax = ;

        if(pRoot->m_pright->m_nMaxLeft > pRoot->m_pright->m_nMaxRight)
            nTempMax = pRoot->m_pright->m_nMaxLeft;
        else
            nTempMax = pRoot->m_pright->m_nMaxRight;

        pRoot->m_nMaxRight = nTempMax + ;
    }

    if(pRoot->m_nMaxLeft + pRoot->m_nMaxRight > nMaxLen)
        nMaxLen = pRoot->m_nMaxLeft + pRoot->m_nMaxRight;   
}



void addBiTreeNode(BiTreeNode *&pCurrent, int value)
{
    if(pCurrent == NULL)
    {
        BiTreeNode *pBiTree = new BiTreeNode();
        pBiTree->m_nValue = value;
        pBiTree->m_pleft = NULL;
        pBiTree->m_pright = NULL;
        pCurrent = pBiTree;
    }
    else
    {
        if((pCurrent->m_nValue) > value)
            addBiTreeNode(pCurrent->m_pleft, value);
        else if((pCurrent->m_nValue) < value)
            addBiTreeNode(pCurrent->m_pright, value);   
    }
}