Stack

Description

• A STACK is an ADT (abstract data type) in LIFO order (last in, first out).
• It has 2 main operations: (1) PUSH for adding, and (2) POP for removing elements.
• It is a protected SINGLY LINKED LIST where PUSH and POP are only allowed on the top front or last element in the stack.
• You may also PEEK to show the last element added.
• Implementation can either be in ARRAY or LINKED LIST.
• It's algorithmic complexity is CONSTANT or O(1).

To Do:

• Implement a STACK using ARRAY that can hold a maximum of 10 string values.
• Create operations PUSH, POP, and PEEK.
• Allow PUSH only if the stack is not yet full.
• Allow POP only if the stack is not yet empty.
• Allow PEEK to see the topmost topmost element.
• Show the updated ARRAY STACK everytime you PUSH or POP.

Pseudocode:

START PROGRAM

 SET capacity, top, stack[]

 PROCEDURE show
  FOR EACH element IN stack.capacity
   PRINT stack[element]

 PROCEDURE isEmpty
  IF stack[0] == null
   PRINT stack is empty
   return TRUE

 PROCEDURE isFull
 IF top == capacity
   PRINT stack is full
   return TRUE

 PROCEDURE push(element)
  IF isFull
   PRINT add failed
  ELSE
   PRINT trying to push on stack[top]
   storage[top] = element
   top++
   PRINT element was successfully added

 PROCEDURE pop
  IF isEmpty
   PRINT remove failed
  ELSE
   PRINT trying to push on stack[top]
   storage[top] = null
   top--
  PRINT storage[top] was successfully removed
  
 PROCEDURE peek
  IF isEmpty
   PRINT NULL
  ELSE 
   PRINT storage[top]

 PROCEDURE main
 // show that stack is empty
 // push 10 integers until stack is full
 // show updated stack
 // try to push again, expect push error message
 // pop last element
 // peek last element
 // pop all elements until stack is empty
 // show updated stack
 // try to pop again, expect pop error message

END PROGRAM