Question

Give the peek algorithm (code) for a Stack that can hold 10 nodes. Include error checking, and assume that the array theData and the integer top are data members of the class Stack.

Give the algorithm for the structure Queue that keeps the front and rear “pointers” from progressing through all of memory (assume the Queue array has n elements).

Answer 1

Give the peek algorithm (code) for a Stack that can hold 10 nodes. Include error
checking, and assume that the array -theData- and the integer -top- are data members of
the class -Stack.

Algorithm peek(Stack stk)
//Input: Stack stk which is an array of 10 nodes, and the top pointing to top element of the stk.
//Output: The top element of the stack, if it exists. null otherwise.
//Given the Stack stk, will check if there are elements in the stack, and if there are....
//Will return the top element of the stack, and if there are not.... will return null.
//Note that this algorithm doesn't modify the Stack by any means....
   if(stk.top == -1)   //This is how an empty stack in the array representation is used.
       return NULL;
   else
       return stk.theData[top]  

=================================================================================

Give the algorithm for the structure -Queue- that keeps the front and rear "pointers"
from progressing through all of memory (assume the Queue array has n elements).

Algorithm isFull(Queue que)
//Input: Queue que which is an array of n elements, and rear pointing to the recently inserted
//       element in the array, and front pointing to the first element in the Queue.
//Output: Returns true if que is full, and false otherwise.
//Given the queue, if it is full, returns true, and false otherwise. This helps in
//keeping the rear from going beyond the allocation.
   if(rear == n)
       return true;
   else
       return false;  
Algorithm isEmpty(Queue que)
//Input: Queue que which is an array of n elements, and rear pointing to the recently inserted
//       element in the array, and front pointing to the first element in the Queue.
//Output: Returns true if que is empty, and false otherwise.
//Given the queue, if it is empty, returns true, and false otherwise. This helps in
//keeping the front from going beyond the allocation.
   if(rear == front)
       return true;
   else
       return false;

Thank you.