#include 
     
      using namespace std;template
      
       struct BinaryTreeNode{                BinaryTreeNode< T>(const T& data)                                :_data( data)                                ,_left( NULL)                                ,_right( NULL)                {}                 T _data;                 BinaryTreeNode
       
        * _left;                 BinaryTreeNode
        
         * _right;};template
         
          class BinaryTree{public:                BinaryTree< T>()                                :_root( NULL)                {}                BinaryTree< T>(const T* a, size_t size)                {                                 size_t index = 0;                                _root = CreateTree( a, index, size );                }                 BinaryTreeNode
          
           * FindGFather(int n1, int n2)                {                                 return _FindGFather(_root, n1 , n2);                }                 void PreOrder()                {                                _PreOrder(_root);                                cout<
           
            
             * CreateTree(const T* a, size_t& index, size_t size)                {                                 BinaryTreeNode
             
              * root = NULL;                                 if ((index < size) && ( a[index ] != '#'))                                {                                                root= new BinaryTreeNode 
              
               (a[index]);                                                root->_left=CreateTree( a, ++index , size);                                                root->_right=CreateTree( a, ++index , size);                                }                                 return root;                }                 //看数字n在不在root这棵树里边                 bool IsOfTree(BinaryTreeNode 
               
                * root, int n)                {                                 if(root ==NULL)                                                 return false ;                                 else if (root->_data== n)                                                 return true ;                                 else                                                 return (IsOfTree(root ->_left,n) || IsOfTree( root->_right, n ));                }                 BinaryTreeNode
                
                 * _FindGFather(BinaryTreeNode< T>* root , int n1, int n2)                {                                 if(IsOfTree(root , n1) && IsOfTree( root, n2 ))  //n1和n2都在这棵树里边，继续往下                                {                                                 if(IsOfTree(root ->_left, n1) && (IsOfTree( root->_left, n2 )))                                                                 return _FindGFather(root ->_left, n1, n2);                                                 else if (IsOfTree(root->_right, n1) && (root ->_right, n2))                                                                 return _FindGFather(root ->_right, n1, n2);                                                 else                                                                 return root ;  //n1和n2在不同的子树里边，返回上一级；或者n1是n2的父亲（n2是n1的父亲），就返回父亲的值                                }                                 else                                                 return NULL ;                }                 void _PreOrder(BinaryTreeNode 
                 
                  * root)                {                                 if(root ==NULL)                                                 return;                                cout<< root->_data<<" " ;                                _PreOrder( root->_left);                                _PreOrder( root->_right);                }protected:                 BinaryTreeNode
                  
                   * _root;};void test(){                 int arr[]={20, 18, 21, '#' , '#', 5, 7, '#', 3, '#' ,'#', 12, '#', '#' , 6};                 BinaryTree
                   
                     t(arr,sizeof(arr)/ sizeof(arr[0]));                t.PreOrder();                 BinaryTreeNode
                    
                     * ret = t.FindGFather(21, 12);                cout<
                     
                      _data<