bool HasSubtree(TreeNode* pRoot1, TreeNode* pRoot2){        if (pRoot1 == NULL) return false;//这一点很重要，要不然if (pRoot1->val == pRoot2->val)会报空指针的错误        if (pRoot2 == NULL) return false;                bool res = false;                if(pRoot1->val == pRoot2->val){            res = DoseTree1HasTree2(pRoot1,pRoot2);        }        if(!res){            res = DoseTree1HasTree2(pRoot1->left,pRoot2);        }        if(!res){            res = DoseTree1HasTree2(pRoot1->right,pRoot2);        }        return res;    }       bool DoseTree1HasTree2(TreeNode* tree1, TreeNode* tree2)    {        if (tree1 == NULL &&tree2 == NULL) return true;//tree1和tree2都为空        else if (tree1 == NULL && tree2!=NULL) return false;        else if (tree1 != NULL && tree2==NULL) return true;        else         {            if (tree1->val != tree2->val) return false;            return DoseTree1HasTree2(tree1->left, tree2->left) && DoseTree1HasTree2(tree1->right, tree2->right);        }            }

树的子结构