交换二叉树的左右子树

root是根节点
BiNode * temp, * root1;
void swap(BiNode root1){
    if(root1 == NULL) return;
        else{
        temp = root1->lchild;
        root1->lchild = root1->rchild;
        root1->rchild = temp;
        swap(root1->lchild);
        swap(root1->rchild);
    }
}