树T1交换其（某些）左右节点的左右儿子变换成树T2，则是同构。给出一个多项式时间算法以决定是否两棵树同构

int IsIsomorphic(SearchTree t1, SearchTree t2) {
if (t1&&t2) {
if (t1->element != t2->element)
return 0;
return (isomorphic(t1->left, t2->left) && isomorphic(t1->right, t2->right)) || (isomorphic(t1->left, t2->right) && isomorphic(t1->right, t2->left));
}
else {
return t1 == NULL&&t2 == NULL;
}
}