Array-based Stack Implementation Logic - Educational Content

The stack's restricted access, mandated by the FILO principle, is strictly enforced through a standardized set of procedures.

All primary stack manipulation operations center around updating the top index, which maintains the state of the stack.
The five fundamental stack operations are:

Primary Operations (Manipulation):

push: Inserts a new element at the index $top + 1$.
pop: Removes the element currently pointed to by top and then decrements the pointer.

Helper Operations (Status Checks):

peek (or top): Returns the value at the current top position without removing it.
isEmpty: A check ensuring no underflow occurs ($top == -1$).
isFull: A check ensuring no overflow occurs ($top == n - 1$).

Fundamental Stack Operations

Operation	Description
`push(element)`	Adds an element to the top of the stack.
`pop()`	Removes and returns the top element.
`peek()`	Returns the top element without removing it.
`isEmpty()`	Checks if the stack is empty.
`isFull()`	Checks if the stack has reached its capacity.

Array-based Stack Implementation Logic (Python)

1# Array-based Stack Implementation Logic
2n = 4 # Capacity (Global Definition n)
3stack = [None] * n
4top = -1 # Global Definition top
5
6def isFull(t):
7    return t == n - 1
8
9# Push Logic (Add 10)
10element_A = 10
11if not isFull(top):
12    top += 1 # Increments top index
13    stack[top] = element_A
14
15# Push Logic (Add 20)
16element_B = 20
17if not isFull(top):
18    top += 1 
19    stack[top] = element_B
20    
21# Pop Logic
22if top != -1: 
23    removed_element = stack[top]
24    stack[top] = None # Clears cell
25    top -= 1 # Decrements top index
26    
27print(f"Current top index after operations: {top}")

Knowledge Check

In an array-based stack of capacity 4, if `top` is initially -1, what is the value of `top` after two `push` operations?

A) 0
B) 1
C) 2