树的子结构

　　题目：输入两颗二叉树A和B，判断B是不是A的子结构。二叉树的定义如下：

struct TreeNode{
    int val;
    TreeNode* left;
    TreeNode* right;
};

    代码如下：

 bool HasSubtree(TreeNode* pRoot1, TreeNode* pRoot2)
    {
        bool result = false;
        if(pRoot1!=NULL&&pRoot2!=NULL){
            if(pRoot1->val == pRoot2->val)
                result = DoesTree1HaveTree2(pRoot1,pRoot2);
            if(!result)
                result = HasSubtree(pRoot1->left,pRoot2);
            if(!result)
                result = HasSubtree(pRoot1->right,pRoot2);
        }
        return result;

    }
    
    bool DoesTree1HaveTree2(TreeNode* pRoot1,TreeNode* pRoot2){
        if(pRoot2==NULL)
            return true;
        if(pRoot1==NULL)
            return false;
        if(pRoot1->val != pRoot2->val)
            return false;
        return DoesTree1HaveTree2(pRoot1->left,pRoot2->left)&&DoesTree1HaveTree2(pRoot1->right,pRoot2->right);
    }