下面程序段的功能是实现在二叉排序树中插入一个新结点，请在下划线处填上正确的内容。typedef struct node{int data;struct node *lchild;struct node *rchild;}bitree;void bstinsert(bitree *&t,int k){if (t==0 ) {____________________________;t->data=k;t->lchild=t->rchild=0;}else if (t->data>k) bstinsert(t->lchild,k);else__________________________;}