**1. How do you write a function that can reverse a linked-list? (Cisco System)**

`void reverselist(void)`

{

if(head==0)

return;

if(head->next==0)

return;

if(head->next==tail)

{

head->next = 0;

tail->next = head;

}

else

{

node* pre = head;

node* cur = head->next;

node* curnext = cur->next;

head->next = 0;

cur->next = head;

` for(; curnext!=0; )`

{

cur->next = pre;

pre = cur;

cur = curnext;

curnext = curnext->next;

}

` curnext->next = cur;`

}

}

**2. What is polymorphism?**

Polymorphism is the idea that a base class can be inherited by several classes. A base class pointer can point to its child class and a base class array can store different child class objects.

**3. How do you find out if a linked-list has an end? (i.e. the list is not a cycle)**

You can find out by using 2 pointers. One of them goes 2 nodes each time. The second one goes at 1 nodes each time. If there is a cycle, the one that goes 2 nodes each time will eventually meet the one that goes slower. If that is the case, then you will know the linked-list is a cycle.

**4. How can you tell what shell you are running on UNIX system?**

You can do the Echo $RANDOM. It will return a undefined variable if you are from the C-Shell, just a return prompt if you are from the Bourne shell, and a 5 digit random numbers if you are from the Korn shell. You could also do a ps -l and look for the shell with the highest PID.

**5. What is Boyce Codd Normal form? **

A relation schema R is in BCNF with respect to a set F of functional dependencies if for all functional dependencies in F+ of the form a->b, where a and b is a subset of R, at least one of the following holds:

- a->b is a trivial functional dependency (b is a subset of a)
- a is a superkey for schema R

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